diff --git a/backend/src/index.ts b/backend/src/index.ts
index 2aa7b07e..3b4cab2d 100644
--- a/backend/src/index.ts
+++ b/backend/src/index.ts
@@ -9,6 +9,7 @@ import { resolvers } from "~/schema/resolvers.generated";
 import { fromNodeHeaders, toNodeHandler } from "better-auth/node";
 import { auth } from "~/auth";
 import { createBookGenresLoader } from "~/schema/loaders";
+import { maxAliasesRule } from "~/schema/requestLimits";
 
 export interface ApolloContext {
   session: Awaited<ReturnType<typeof auth.api.getSession>>;
@@ -31,6 +32,7 @@ const server = new ApolloServer<ApolloContext>({
   typeDefs,
   resolvers,
   plugins: [ApolloServerPluginDrainHttpServer({ httpServer })],
+  validationRules: [maxAliasesRule],
 });
 
 await server.start();
diff --git a/backend/src/schema/books/resolvers/Query/searchBooks.ts b/backend/src/schema/books/resolvers/Query/searchBooks.ts
index 288be837..60a680dd 100644
--- a/backend/src/schema/books/resolvers/Query/searchBooks.ts
+++ b/backend/src/schema/books/resolvers/Query/searchBooks.ts
@@ -13,19 +13,34 @@ import {
 } from "drizzle-orm";
 import { GraphQLError } from "graphql/error";
 import { db } from "~/db";
+import { assertLimit, assertOffset } from "~/schema/pagination";
 import { bookGenres, books, bookToGenres } from "~/db/schema";
 import type { QueryResolvers } from "~/schema/types.generated";
 
+const MAX_GENRES = 15;
+const MAX_TEXT_LENGTH = 200;
+
 export const searchBooks: NonNullable<QueryResolvers["searchBooks"]> = async (
   _parent,
   args,
 ) => {
-  if (args.limit < 0 || args.offset < 0) {
-    throw new GraphQLError("Limit and offset cannot be negative.", {
+  assertLimit(args.limit);
+  assertOffset(args.offset);
+
+  if (args.genres && args.genres.length > MAX_GENRES) {
+    throw new GraphQLError(`You may only select up to ${MAX_GENRES} genres.`, {
       extensions: { code: "BAD_USER_INPUT" },
     });
   }
 
+  const texts = [args.title, args.series, args.author, args.publisher];
+  if (texts.some((text) => text && text.length > MAX_TEXT_LENGTH)) {
+    throw new GraphQLError(
+      `Search text may only be up to ${MAX_TEXT_LENGTH} characters.`,
+      { extensions: { code: "BAD_USER_INPUT" } },
+    );
+  }
+
   const conditions: SQL[] = [];
 
   if (args.title && args.fuzzy) {
diff --git a/backend/src/schema/books/schema.graphql b/backend/src/schema/books/schema.graphql
index fc36ebe8..a240b27c 100644
--- a/backend/src/schema/books/schema.graphql
+++ b/backend/src/schema/books/schema.graphql
@@ -36,7 +36,7 @@ extend type Query {
   searchBooks(
     title: String
     "Match titles that are similar to the title, for example with typos, ordered by similarity"
-    fuzzy: Boolean = false
+    fuzzy: Boolean! = false
     series: String
     author: String
     language: String
@@ -46,10 +46,10 @@ extend type Query {
     minPages: Int
     maxPages: Int
     minRatings: Int
-    limit: Int = 12
-    offset: Int = 0
-    sortBy: BookSortField = ID
-    sortDirection: SortDirection = ASC
+    limit: Int! = 12
+    offset: Int! = 0
+    sortBy: BookSortField! = ID
+    sortDirection: SortDirection! = ASC
   ): BookSearchResult!
 }
 
diff --git a/backend/src/schema/favorites/resolvers/Query/favoriteBooks.ts b/backend/src/schema/favorites/resolvers/Query/favoriteBooks.ts
index 041355ed..7e5fb0a4 100644
--- a/backend/src/schema/favorites/resolvers/Query/favoriteBooks.ts
+++ b/backend/src/schema/favorites/resolvers/Query/favoriteBooks.ts
@@ -2,6 +2,7 @@ import { GraphQLError } from "graphql/error";
 import { eq } from "drizzle-orm";
 import type { QueryResolvers } from "~/schema/types.generated";
 import { db } from "~/db";
+import { assertLimit, assertOffset } from "~/schema/pagination";
 import { favoriteBooks as favoriteBooksTable } from "~/db/schema";
 
 export const favoriteBooks: NonNullable<
@@ -16,11 +17,8 @@ export const favoriteBooks: NonNullable<
     );
   }
 
-  if (arg.limit < 0 || arg.offset < 0) {
-    throw new GraphQLError("Limit and offset cannot be negative.", {
-      extensions: { code: "BAD_USER_INPUT" },
-    });
-  }
+  assertLimit(arg.limit);
+  assertOffset(arg.offset);
 
   const [foundBooks, totalCount] = await Promise.all([
     db.query.favoriteBooks.findMany({
diff --git a/backend/src/schema/favorites/resolvers/Query/favoriteGenres.ts b/backend/src/schema/favorites/resolvers/Query/favoriteGenres.ts
index 2a7d1625..d03d0c0c 100644
--- a/backend/src/schema/favorites/resolvers/Query/favoriteGenres.ts
+++ b/backend/src/schema/favorites/resolvers/Query/favoriteGenres.ts
@@ -2,6 +2,7 @@ import { GraphQLError } from "graphql/error";
 import { asc, count, desc, eq } from "drizzle-orm";
 import type { QueryResolvers } from "~/schema/types.generated";
 import { db } from "~/db";
+import { assertLimit } from "~/schema/pagination";
 import { bookGenres, bookToGenres, favoriteBooks } from "~/db/schema";
 
 export const favoriteGenres: NonNullable<
@@ -16,6 +17,8 @@ export const favoriteGenres: NonNullable<
     );
   }
 
+  assertLimit(arg.limit);
+
   const genres = await db
     .select({ genre: bookGenres.genre })
     .from(favoriteBooks)
diff --git a/backend/src/schema/favorites/schema.graphql b/backend/src/schema/favorites/schema.graphql
index 87732cd4..f5fad9d9 100644
--- a/backend/src/schema/favorites/schema.graphql
+++ b/backend/src/schema/favorites/schema.graphql
@@ -1,10 +1,10 @@
 extend type Query {
   "Favorite books of the logged-in user, newest first."
-  favoriteBooks(limit: Int = 12, offset: Int = 0): BookSearchResult!
+  favoriteBooks(limit: Int! = 12, offset: Int! = 0): BookSearchResult!
   "ID of every book the logged-in user that has been added to their favorites."
   favoriteBookIds: [Int!]!
   "The logged-in user's most common genres among their favorite books."
-  favoriteGenres(limit: Int = 3): [String!]!
+  favoriteGenres(limit: Int! = 3): [String!]!
 }
 
 extend type Mutation {
diff --git a/backend/src/schema/pagination.ts b/backend/src/schema/pagination.ts
new file mode 100644
index 00000000..2c6476d1
--- /dev/null
+++ b/backend/src/schema/pagination.ts
@@ -0,0 +1,27 @@
+import { GraphQLError } from "graphql/error";
+
+const MAX_LIMIT = 100;
+
+function assertLimit(limit: number) {
+  if (limit < 0) {
+    throw new GraphQLError("Limit cannot be negative.", {
+      extensions: { code: "BAD_USER_INPUT" },
+    });
+  }
+
+  if (limit > MAX_LIMIT) {
+    throw new GraphQLError(`Limit must be at most ${MAX_LIMIT}.`, {
+      extensions: { code: "BAD_USER_INPUT" },
+    });
+  }
+}
+
+function assertOffset(offset: number) {
+  if (offset < 0) {
+    throw new GraphQLError("Offset cannot be negative.", {
+      extensions: { code: "BAD_USER_INPUT" },
+    });
+  }
+}
+
+export { assertLimit, assertOffset };
diff --git a/backend/src/schema/requestLimits.ts b/backend/src/schema/requestLimits.ts
new file mode 100644
index 00000000..4aeeeaf5
--- /dev/null
+++ b/backend/src/schema/requestLimits.ts
@@ -0,0 +1,31 @@
+import { GraphQLError, type ASTVisitor, type ValidationContext } from "graphql";
+
+const MAX_ALIASES = 10;
+
+// The same field can only be requested several times in one operation by
+// giving each copy an alias, e.g. `a: searchBooks(limit: 100) b: searchBooks(...)`.
+// We should therefore limit the number of aliases to prevent abuse,
+// e.g. a single request fetching multiple thousand rows.
+function maxAliasesRule(context: ValidationContext): ASTVisitor {
+  let aliases = 0;
+
+  return {
+    Field(node) {
+      if (node.alias) aliases++;
+    },
+    Document: {
+      leave() {
+        if (aliases > MAX_ALIASES) {
+          // Apollo Server responds with GRAPHQL_VALIDATION_FAILED and HTTP 400
+          context.reportError(
+            new GraphQLError(
+              `Operation may use at most ${MAX_ALIASES} aliases, found ${aliases}.`,
+            ),
+          );
+        }
+      },
+    },
+  };
+}
+
+export { maxAliasesRule };
diff --git a/backend/src/schema/schema.generated.graphqls b/backend/src/schema/schema.generated.graphqls
index 30f11856..e51b58d5 100644
--- a/backend/src/schema/schema.generated.graphqls
+++ b/backend/src/schema/schema.generated.graphqls
@@ -42,10 +42,10 @@ type Query {
   favoriteBookIds: [Int!]!
 
   """Favorite books of the logged-in user, newest first."""
-  favoriteBooks(limit: Int = 12, offset: Int = 0): BookSearchResult!
+  favoriteBooks(limit: Int! = 12, offset: Int! = 0): BookSearchResult!
 
   """The logged-in user's most common genres among their favorite books."""
-  favoriteGenres(limit: Int = 3): [String!]!
+  favoriteGenres(limit: Int! = 3): [String!]!
   genres: [String!]!
   languages: [String!]!
   searchBooks(
@@ -55,18 +55,18 @@ type Query {
     """
     Match titles that are similar to the title, for example with typos, ordered by similarity
     """
-    fuzzy: Boolean = false
+    fuzzy: Boolean! = false
     genres: [String!]
     language: String
-    limit: Int = 12
+    limit: Int! = 12
     maxPages: Int
     minPages: Int
     minRatings: Int
-    offset: Int = 0
+    offset: Int! = 0
     publisher: String
     series: String
-    sortBy: BookSortField = ID
-    sortDirection: SortDirection = ASC
+    sortBy: BookSortField! = ID
+    sortDirection: SortDirection! = ASC
     title: String
   ): BookSearchResult!
 }
diff --git a/backend/src/schema/typeDefs.generated.ts b/backend/src/schema/typeDefs.generated.ts
index 3f3eeb3b..8f3cb3e2 100644
--- a/backend/src/schema/typeDefs.generated.ts
+++ b/backend/src/schema/typeDefs.generated.ts
@@ -1,2 +1,2 @@
 import type { DocumentNode } from 'graphql';
-  export const typeDefs = {"kind":"Document","definitions":[{"name":{"kind":"Name","value":"Query"},"kind":"ObjectTypeDefinition","fields":[{"kind":"FieldDefinition","name":{"kind":"Name","value":"book"},"arguments":[{"kind":"InputValueDefinition","name":{"kind":"Name","value":"id"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}}}],"type":{"kind":"NamedType","name":{"kind":"Name","value":"Book"}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"genres"},"type":{"kind":"NonNullType","type":{"kind":"ListType","type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"languages"},"type":{"kind":"NonNullType","type":{"kind":"ListType","type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"bookFormats"},"type":{"kind":"NonNullType","type":{"kind":"ListType","type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"searchBooks"},"arguments":[{"kind":"InputValueDefinition","name":{"kind":"Name","value":"title"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"InputValueDefinition","description":{"kind":"StringValue","value":"Match titles that are similar to the title, for example with typos, ordered by similarity","block":false},"name":{"kind":"Name","value":"fuzzy"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"Boolean"}},"defaultValue":{"kind":"BooleanValue","value":false}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"series"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"author"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"language"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"bookFormat"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"publisher"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"genres"},"type":{"kind":"ListType","type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}}}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"minPages"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"maxPages"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"minRatings"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"limit"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}},"defaultValue":{"kind":"IntValue","value":"12"}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"offset"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}},"defaultValue":{"kind":"IntValue","value":"0"}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"sortBy"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"BookSortField"}},"defaultValue":{"kind":"EnumValue","value":"ID"}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"sortDirection"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"SortDirection"}},"defaultValue":{"kind":"EnumValue","value":"ASC"}}],"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"BookSearchResult"}}}},{"kind":"FieldDefinition","description":{"kind":"StringValue","value":"Favorite books of the logged-in user, newest first.","block":false},"name":{"kind":"Name","value":"favoriteBooks"},"arguments":[{"kind":"InputValueDefinition","name":{"kind":"Name","value":"limit"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}},"defaultValue":{"kind":"IntValue","value":"12"}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"offset"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}},"defaultValue":{"kind":"IntValue","value":"0"}}],"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"BookSearchResult"}}}},{"kind":"FieldDefinition","description":{"kind":"StringValue","value":"ID of every book the logged-in user that has been added to their favorites.","block":false},"name":{"kind":"Name","value":"favoriteBookIds"},"type":{"kind":"NonNullType","type":{"kind":"ListType","type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}}}}},{"kind":"FieldDefinition","description":{"kind":"StringValue","value":"The logged-in user's most common genres among their favorite books.","block":false},"name":{"kind":"Name","value":"favoriteGenres"},"arguments":[{"kind":"InputValueDefinition","name":{"kind":"Name","value":"limit"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}},"defaultValue":{"kind":"IntValue","value":"3"}}],"type":{"kind":"NonNullType","type":{"kind":"ListType","type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}}}}}],"directives":[],"interfaces":[]},{"name":{"kind":"Name","value":"Mutation"},"kind":"ObjectTypeDefinition","fields":[{"kind":"FieldDefinition","name":{"kind":"Name","value":"addFavoriteBook"},"arguments":[{"kind":"InputValueDefinition","name":{"kind":"Name","value":"bookId"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}}}],"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Book"}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"removeFavoriteBook"},"arguments":[{"kind":"InputValueDefinition","name":{"kind":"Name","value":"bookId"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}}}],"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Boolean"}}}}],"directives":[],"interfaces":[]},{"kind":"ObjectTypeDefinition","name":{"kind":"Name","value":"Book"},"fields":[{"kind":"FieldDefinition","name":{"kind":"Name","value":"id"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"isbn"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"title"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"series"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"author"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"description"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"language"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"bookFormat"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"edition"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"pages"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"publisher"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"publishDate"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"coverImgUrl"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"genres"},"type":{"kind":"NonNullType","type":{"kind":"ListType","type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"rating"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"Float"}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"numRatings"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}}]},{"kind":"EnumTypeDefinition","name":{"kind":"Name","value":"BookSortField"},"values":[{"kind":"EnumValueDefinition","name":{"kind":"Name","value":"ID"}},{"kind":"EnumValueDefinition","name":{"kind":"Name","value":"RATING"}}]},{"kind":"EnumTypeDefinition","name":{"kind":"Name","value":"SortDirection"},"values":[{"kind":"EnumValueDefinition","name":{"kind":"Name","value":"ASC"}},{"kind":"EnumValueDefinition","name":{"kind":"Name","value":"DESC"}}]},{"kind":"ObjectTypeDefinition","name":{"kind":"Name","value":"BookSearchResult"},"fields":[{"kind":"FieldDefinition","name":{"kind":"Name","value":"books"},"type":{"kind":"NonNullType","type":{"kind":"ListType","type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Book"}}}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"totalCount"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}}}]},{"kind":"SchemaDefinition","operationTypes":[{"kind":"OperationTypeDefinition","type":{"kind":"NamedType","name":{"kind":"Name","value":"Query"}},"operation":"query"},{"kind":"OperationTypeDefinition","type":{"kind":"NamedType","name":{"kind":"Name","value":"Mutation"}},"operation":"mutation"}]}]} as unknown as DocumentNode
\ No newline at end of file
+  export const typeDefs = {"kind":"Document","definitions":[{"name":{"kind":"Name","value":"Query"},"kind":"ObjectTypeDefinition","fields":[{"kind":"FieldDefinition","name":{"kind":"Name","value":"book"},"arguments":[{"kind":"InputValueDefinition","name":{"kind":"Name","value":"id"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}}}],"type":{"kind":"NamedType","name":{"kind":"Name","value":"Book"}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"genres"},"type":{"kind":"NonNullType","type":{"kind":"ListType","type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"languages"},"type":{"kind":"NonNullType","type":{"kind":"ListType","type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"bookFormats"},"type":{"kind":"NonNullType","type":{"kind":"ListType","type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"searchBooks"},"arguments":[{"kind":"InputValueDefinition","name":{"kind":"Name","value":"title"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"InputValueDefinition","description":{"kind":"StringValue","value":"Match titles that are similar to the title, for example with typos, ordered by similarity","block":false},"name":{"kind":"Name","value":"fuzzy"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Boolean"}}},"defaultValue":{"kind":"BooleanValue","value":false}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"series"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"author"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"language"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"bookFormat"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"publisher"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"genres"},"type":{"kind":"ListType","type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}}}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"minPages"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"maxPages"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"minRatings"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"limit"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}},"defaultValue":{"kind":"IntValue","value":"12"}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"offset"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}},"defaultValue":{"kind":"IntValue","value":"0"}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"sortBy"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"BookSortField"}}},"defaultValue":{"kind":"EnumValue","value":"ID"}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"sortDirection"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"SortDirection"}}},"defaultValue":{"kind":"EnumValue","value":"ASC"}}],"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"BookSearchResult"}}}},{"kind":"FieldDefinition","description":{"kind":"StringValue","value":"Favorite books of the logged-in user, newest first.","block":false},"name":{"kind":"Name","value":"favoriteBooks"},"arguments":[{"kind":"InputValueDefinition","name":{"kind":"Name","value":"limit"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}},"defaultValue":{"kind":"IntValue","value":"12"}},{"kind":"InputValueDefinition","name":{"kind":"Name","value":"offset"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}},"defaultValue":{"kind":"IntValue","value":"0"}}],"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"BookSearchResult"}}}},{"kind":"FieldDefinition","description":{"kind":"StringValue","value":"ID of every book the logged-in user that has been added to their favorites.","block":false},"name":{"kind":"Name","value":"favoriteBookIds"},"type":{"kind":"NonNullType","type":{"kind":"ListType","type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}}}}},{"kind":"FieldDefinition","description":{"kind":"StringValue","value":"The logged-in user's most common genres among their favorite books.","block":false},"name":{"kind":"Name","value":"favoriteGenres"},"arguments":[{"kind":"InputValueDefinition","name":{"kind":"Name","value":"limit"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}},"defaultValue":{"kind":"IntValue","value":"3"}}],"type":{"kind":"NonNullType","type":{"kind":"ListType","type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}}}}}],"directives":[],"interfaces":[]},{"name":{"kind":"Name","value":"Mutation"},"kind":"ObjectTypeDefinition","fields":[{"kind":"FieldDefinition","name":{"kind":"Name","value":"addFavoriteBook"},"arguments":[{"kind":"InputValueDefinition","name":{"kind":"Name","value":"bookId"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}}}],"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Book"}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"removeFavoriteBook"},"arguments":[{"kind":"InputValueDefinition","name":{"kind":"Name","value":"bookId"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}}}],"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Boolean"}}}}],"directives":[],"interfaces":[]},{"kind":"ObjectTypeDefinition","name":{"kind":"Name","value":"Book"},"fields":[{"kind":"FieldDefinition","name":{"kind":"Name","value":"id"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"isbn"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"title"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"series"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"author"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"description"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"language"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"bookFormat"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"edition"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"pages"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"publisher"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"publishDate"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"coverImgUrl"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"genres"},"type":{"kind":"NonNullType","type":{"kind":"ListType","type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"String"}}}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"rating"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"Float"}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"numRatings"},"type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}}]},{"kind":"EnumTypeDefinition","name":{"kind":"Name","value":"BookSortField"},"values":[{"kind":"EnumValueDefinition","name":{"kind":"Name","value":"ID"}},{"kind":"EnumValueDefinition","name":{"kind":"Name","value":"RATING"}}]},{"kind":"EnumTypeDefinition","name":{"kind":"Name","value":"SortDirection"},"values":[{"kind":"EnumValueDefinition","name":{"kind":"Name","value":"ASC"}},{"kind":"EnumValueDefinition","name":{"kind":"Name","value":"DESC"}}]},{"kind":"ObjectTypeDefinition","name":{"kind":"Name","value":"BookSearchResult"},"fields":[{"kind":"FieldDefinition","name":{"kind":"Name","value":"books"},"type":{"kind":"NonNullType","type":{"kind":"ListType","type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Book"}}}}}},{"kind":"FieldDefinition","name":{"kind":"Name","value":"totalCount"},"type":{"kind":"NonNullType","type":{"kind":"NamedType","name":{"kind":"Name","value":"Int"}}}}]},{"kind":"SchemaDefinition","operationTypes":[{"kind":"OperationTypeDefinition","type":{"kind":"NamedType","name":{"kind":"Name","value":"Query"}},"operation":"query"},{"kind":"OperationTypeDefinition","type":{"kind":"NamedType","name":{"kind":"Name","value":"Mutation"}},"operation":"mutation"}]}]} as unknown as DocumentNode
\ No newline at end of file
diff --git a/backend/src/schema/types.generated.ts b/backend/src/schema/types.generated.ts
index 29d54c4d..53afedaa 100644
--- a/backend/src/schema/types.generated.ts
+++ b/backend/src/schema/types.generated.ts
@@ -83,31 +83,31 @@ export type QuerybookArgs = {
 
 
 export type QueryfavoriteBooksArgs = {
-  limit?: InputMaybe<Scalars['Int']['input']>;
-  offset?: InputMaybe<Scalars['Int']['input']>;
+  limit?: Scalars['Int']['input'];
+  offset?: Scalars['Int']['input'];
 };
 
 
 export type QueryfavoriteGenresArgs = {
-  limit?: InputMaybe<Scalars['Int']['input']>;
+  limit?: Scalars['Int']['input'];
 };
 
 
 export type QuerysearchBooksArgs = {
   author?: InputMaybe<Scalars['String']['input']>;
   bookFormat?: InputMaybe<Scalars['String']['input']>;
-  fuzzy?: InputMaybe<Scalars['Boolean']['input']>;
+  fuzzy?: Scalars['Boolean']['input'];
   genres?: InputMaybe<Array<Scalars['String']['input']>>;
   language?: InputMaybe<Scalars['String']['input']>;
-  limit?: InputMaybe<Scalars['Int']['input']>;
+  limit?: Scalars['Int']['input'];
   maxPages?: InputMaybe<Scalars['Int']['input']>;
   minPages?: InputMaybe<Scalars['Int']['input']>;
   minRatings?: InputMaybe<Scalars['Int']['input']>;
-  offset?: InputMaybe<Scalars['Int']['input']>;
+  offset?: Scalars['Int']['input'];
   publisher?: InputMaybe<Scalars['String']['input']>;
   series?: InputMaybe<Scalars['String']['input']>;
-  sortBy?: InputMaybe<BookSortField>;
-  sortDirection?: InputMaybe<SortDirection>;
+  sortBy?: BookSortField;
+  sortDirection?: SortDirection;
   title?: InputMaybe<Scalars['String']['input']>;
 };
 
diff --git a/frontend/app/api/types/graphql.generated.ts b/frontend/app/api/types/graphql.generated.ts
index af2915fa..615c9434 100644
--- a/frontend/app/api/types/graphql.generated.ts
+++ b/frontend/app/api/types/graphql.generated.ts
@@ -23,8 +23,8 @@ export type BookFiltersQueryVariables = Exact<{ [key: string]: never; }>;
 export type BookFiltersQuery = { genres: Array<string>, languages: Array<string>, bookFormats: Array<string> };
 
 export type FavoriteBooksQueryVariables = Exact<{
-  limit?: number | null | undefined;
-  offset?: number | null | undefined;
+  limit: number;
+  offset: number;
 }>;
 
 
@@ -51,17 +51,17 @@ export type RemoveFavoriteBookMutation = { removeFavoriteBook: boolean };
 
 export type SearchBooksQueryVariables = Exact<{
   title?: string | null | undefined;
-  fuzzy?: boolean | null | undefined;
+  fuzzy?: boolean;
   genres?: Array<string> | string | null | undefined;
   language?: string | null | undefined;
   bookFormat?: string | null | undefined;
   minPages?: number | null | undefined;
   maxPages?: number | null | undefined;
   minRatings?: number | null | undefined;
-  sortBy?: BookSortField | null | undefined;
-  sortDirection?: SortDirection | null | undefined;
-  limit?: number | null | undefined;
-  offset?: number | null | undefined;
+  sortBy?: BookSortField;
+  sortDirection?: SortDirection;
+  limit: number;
+  offset: number;
 }>;
 
 
diff --git a/frontend/app/components/books/BookFilters/BookFilters.test.tsx b/frontend/app/components/books/BookFilters/BookFilters.test.tsx
index afb84f0d..d66329d0 100644
--- a/frontend/app/components/books/BookFilters/BookFilters.test.tsx
+++ b/frontend/app/components/books/BookFilters/BookFilters.test.tsx
@@ -3,6 +3,7 @@ import { render, screen, waitFor } from "@testing-library/react";
 import userEvent from "@testing-library/user-event";
 import { createRoutesStub, Link, useSearchParams } from "react-router";
 import { BookFilters } from "~/components/books/BookFilters/BookFilters";
+import { toast } from "~/components/ui/Toast";
 
 vi.mock("~/hooks/useBookFilters", () => ({
   useBookFilters: () => ({
@@ -65,6 +66,26 @@ describe("FilterBooksSection", () => {
     );
   });
 
+  it("shows an error and keeps the genres when selecting more than 15", async () => {
+    const addToast = vi.spyOn(toast, "add");
+    const user = userEvent.setup();
+    const fifteenGenres = Array.from({ length: 15 }, (_, i) => `Genre${i}`);
+    const query = fifteenGenres.map((genre) => `genres=${genre}`).join("&");
+    render(<Stub initialEntries={[`/?${query}`]} />);
+
+    await user.type(screen.getByLabelText("Genres"), "Sci");
+    await user.click(
+      await screen.findByRole("option", { name: "Science Fiction" }),
+    );
+
+    expect(addToast).toHaveBeenCalledWith(
+      expect.objectContaining({ type: "error" }),
+    );
+    expect(screen.getByTestId("genres")).toHaveTextContent(
+      fifteenGenres.join(","),
+    );
+  });
+
   it("shows the selected language from the URL", () => {
     render(<Stub initialEntries={["/?language=French"]} />);
 
diff --git a/frontend/app/components/books/BookFilters/BookFilters.tsx b/frontend/app/components/books/BookFilters/BookFilters.tsx
index 790a7bbc..46a77b52 100644
--- a/frontend/app/components/books/BookFilters/BookFilters.tsx
+++ b/frontend/app/components/books/BookFilters/BookFilters.tsx
@@ -17,6 +17,8 @@ import {
 } from "~/components/ui/Combobox";
 import { MinRatingsFilter } from "~/components/books/MinRatingsFilter/MinRatingsFilter";
 import { PagesFilter } from "~/components/books/PagesFilter/PagesFilter";
+import { toast } from "~/components/ui/Toast";
+import { MAX_GENRES } from "~/lib/constants";
 
 function BookFilters() {
   const [, setSearchParams] = useSearchParams();
@@ -65,6 +67,13 @@ function BookFilters() {
             items={genres}
             value={filters.genres ?? []}
             onValueChange={(selected) => {
+              if (selected.length > MAX_GENRES) {
+                toast.add({
+                  description: `You can select up to ${MAX_GENRES} genres.`,
+                  type: "error",
+                });
+                return;
+              }
               setSearchParams((searchParams) => {
                 searchParams.delete("genres");
                 selected.forEach((genre) =>
diff --git a/frontend/app/components/books/SearchBar/SearchBar.test.tsx b/frontend/app/components/books/SearchBar/SearchBar.test.tsx
index 75e0eeba..8b6e0e0b 100644
--- a/frontend/app/components/books/SearchBar/SearchBar.test.tsx
+++ b/frontend/app/components/books/SearchBar/SearchBar.test.tsx
@@ -1,7 +1,8 @@
-import { describe, expect, it } from "vitest";
+import { describe, expect, it, vi } from "vitest";
 import { render, screen, waitFor } from "@testing-library/react";
 import userEvent from "@testing-library/user-event";
 import { SearchBar } from "~/components/books/SearchBar/SearchBar";
+import { toast } from "~/components/ui/Toast";
 import { createRoutesStub, useSearchParams } from "react-router";
 
 // Shows the current "q" param so tests can assert what SearchBar wrote to the URL.
@@ -50,6 +51,25 @@ describe("SearchBar", () => {
     );
   });
 
+  it("cuts the query at 200 characters and shows an error", async () => {
+    const addToast = vi.spyOn(toast, "add");
+    const user = userEvent.setup();
+    render(<Stub />);
+
+    const searchbox = screen.getByRole("searchbox", {
+      name: "Search for books",
+    });
+    await user.click(searchbox);
+    await user.paste("a".repeat(250));
+    await user.type(searchbox, "b");
+
+    expect(searchbox).toHaveValue("a".repeat(200));
+    expect(addToast).toHaveBeenCalledTimes(1);
+    expect(addToast).toHaveBeenCalledWith(
+      expect.objectContaining({ type: "error" }),
+    );
+  });
+
   it("shows the number of active filters", () => {
     render(<Stub initialEntries={["/?language=English&genres=Fantasy"]} />);
 
diff --git a/frontend/app/components/books/SearchBar/SearchBar.tsx b/frontend/app/components/books/SearchBar/SearchBar.tsx
index 6225530e..4bfa4fc3 100644
--- a/frontend/app/components/books/SearchBar/SearchBar.tsx
+++ b/frontend/app/components/books/SearchBar/SearchBar.tsx
@@ -18,6 +18,8 @@ import {
 import { useSearchParams } from "react-router";
 import { useDebounce } from "~/hooks/useDebounce";
 import { useBookSearchParams } from "~/hooks/useBookSearchParams";
+import { toast } from "~/components/ui/Toast";
+import { MAX_QUERY_LENGTH } from "~/lib/constants";
 
 const SEARCH_DEBOUNCE_MS = 500;
 
@@ -32,6 +34,7 @@ function SearchBar({ resultCount }: SearchBarProps) {
   const [inputField, setInputField] = useState(query);
   const debouncedQuery = useDebounce(inputField, SEARCH_DEBOUNCE_MS);
   const newQueryFromInputRef = useRef(false);
+  const tooLongToastOpenRef = useRef(false);
 
   useEffect(() => {
     if (debouncedQuery !== inputField || debouncedQuery === query) {
@@ -80,8 +83,21 @@ function SearchBar({ resultCount }: SearchBarProps) {
           placeholder="Search books..."
           value={inputField}
           onChange={(e) => {
+            if (
+              e.target.value.length > MAX_QUERY_LENGTH &&
+              !tooLongToastOpenRef.current
+            ) {
+              tooLongToastOpenRef.current = true;
+              toast.add({
+                description: `Search can be at most ${MAX_QUERY_LENGTH} characters.`,
+                type: "error",
+                onClose: () => {
+                  tooLongToastOpenRef.current = false;
+                },
+              });
+            }
             newQueryFromInputRef.current = true;
-            setInputField(e.target.value);
+            setInputField(e.target.value.slice(0, MAX_QUERY_LENGTH));
           }}
         />
 
diff --git a/frontend/app/hooks/useBookSearchParams.test.tsx b/frontend/app/hooks/useBookSearchParams.test.tsx
new file mode 100644
index 00000000..14e531a3
--- /dev/null
+++ b/frontend/app/hooks/useBookSearchParams.test.tsx
@@ -0,0 +1,43 @@
+import { describe, expect, it } from "vitest";
+import { renderHook } from "@testing-library/react";
+import type { ReactNode } from "react";
+import { MemoryRouter } from "react-router";
+import { parsePageNum, useBookSearchParams } from "~/hooks/useBookSearchParams";
+import { MAX_GENRES, MAX_PAGE, MAX_QUERY_LENGTH } from "~/lib/constants";
+
+function renderWithUrl(url: string) {
+  return renderHook(() => useBookSearchParams(), {
+    wrapper: ({ children }: { children: ReactNode }) => (
+      <MemoryRouter initialEntries={[url]}>{children}</MemoryRouter>
+    ),
+  });
+}
+
+describe("parsePageNum", () => {
+  it("falls back to page 1 for missing or invalid values", () => {
+    expect(parsePageNum(null)).toBe(1);
+    expect(parsePageNum("0")).toBe(1);
+    expect(parsePageNum("-3")).toBe(1);
+    expect(parsePageNum("abc")).toBe(1);
+  });
+
+  it("caps the page so the offset fits in a GraphQL Int", () => {
+    expect(parsePageNum("999999999999")).toBe(MAX_PAGE);
+  });
+});
+
+describe("useBookSearchParams", () => {
+  it("cuts a long query from the URL", () => {
+    const { result } = renderWithUrl(`/?q=${"a".repeat(250)}`);
+
+    expect(result.current.query).toBe("a".repeat(MAX_QUERY_LENGTH));
+  });
+
+  it("keeps only the first genres from the URL", () => {
+    const genres = Array.from({ length: 20 }, (_, i) => `Genre${i}`);
+    const query = genres.map((genre) => `genres=${genre}`).join("&");
+    const { result } = renderWithUrl(`/?${query}`);
+
+    expect(result.current.filters.genres).toEqual(genres.slice(0, MAX_GENRES));
+  });
+});
diff --git a/frontend/app/hooks/useBookSearchParams.ts b/frontend/app/hooks/useBookSearchParams.ts
index a8f04d35..6547b8d4 100644
--- a/frontend/app/hooks/useBookSearchParams.ts
+++ b/frontend/app/hooks/useBookSearchParams.ts
@@ -2,6 +2,7 @@ import { useMemo } from "react";
 import { useSearchParams } from "react-router";
 import type { BookFilters } from "~/api/types";
 import { parseBookSort } from "~/api/bookSort";
+import { MAX_GENRES, MAX_PAGE, MAX_QUERY_LENGTH } from "~/lib/constants";
 
 function parseCount(value: string | null) {
   const count = Number(value);
@@ -10,7 +11,7 @@ function parseCount(value: string | null) {
 
 function parsePageNum(value: string | null) {
   const page = Number(value);
-  return Number.isInteger(page) && page >= 1 ? page : 1;
+  return Number.isInteger(page) && page >= 1 ? Math.min(page, MAX_PAGE) : 1;
 }
 
 const FILTER_KEYS = [
@@ -25,13 +26,14 @@ const FILTER_KEYS = [
 function useBookSearchParams() {
   const [searchParams] = useSearchParams();
 
-  const query = searchParams.get("q") ?? "";
+  // Remove any characters above the limit if the user somehow manages to add them
+  const query = (searchParams.get("q") ?? "").slice(0, MAX_QUERY_LENGTH);
   const page = parsePageNum(searchParams.get("page"));
   const sort = parseBookSort(searchParams.get("sort"));
 
   // Only update filters when searchParams change to avoid unnecessary re-renders
   const filters = useMemo((): BookFilters => {
-    const genres = searchParams.getAll("genres");
+    const genres = searchParams.getAll("genres").slice(0, MAX_GENRES);
     const minPages = parseCount(searchParams.get("minPages"));
     const maxPages = parseCount(searchParams.get("maxPages"));
     return {
diff --git a/frontend/app/hooks/useFavoriteBooks.ts b/frontend/app/hooks/useFavoriteBooks.ts
index 987a62e9..2a83091c 100644
--- a/frontend/app/hooks/useFavoriteBooks.ts
+++ b/frontend/app/hooks/useFavoriteBooks.ts
@@ -1,5 +1,5 @@
 import { gql, type TypedDocumentNode } from "@apollo/client";
-import { useMutation, useQuery } from "@apollo/client/react";
+import { skipToken, useMutation, useQuery } from "@apollo/client/react";
 import type {
   AddFavoriteBookMutation,
   AddFavoriteBookMutationVariables,
@@ -17,7 +17,7 @@ const FAVORITE_BOOKS: TypedDocumentNode<
   FavoriteBooksQuery,
   FavoriteBooksQueryVariables
 > = gql`
-  query FavoriteBooks($limit: Int, $offset: Int) {
+  query FavoriteBooks($limit: Int!, $offset: Int!) {
     favoriteBooks(limit: $limit, offset: $offset) {
       totalCount
       books {
@@ -70,12 +70,19 @@ function useFavoriteBooks({
   enabled?: boolean;
   page: number;
 }) {
-  const { data, loading, error } = useQuery(FAVORITE_BOOKS, {
-    variables: { limit: BOOK_PAGE_LIMIT, offset: (page - 1) * BOOK_PAGE_LIMIT },
-    skip: !enabled,
-    // Favorites could be added on other pages, so we want to refetch our favorites when the user visits their profile page.
-    fetchPolicy: "cache-and-network",
-  });
+  const { data, loading, error } = useQuery(
+    FAVORITE_BOOKS,
+    enabled
+      ? {
+          variables: {
+            limit: BOOK_PAGE_LIMIT,
+            offset: (page - 1) * BOOK_PAGE_LIMIT,
+          },
+          // Favorites could be added on other pages, so we want to refetch our favorites when the user visits their profile page.
+          fetchPolicy: "cache-and-network",
+        }
+      : skipToken,
+  );
 
   const books = data?.favoriteBooks.books.map((book) => {
     // Extract only the fields we modify, keep the rest in ...rest
diff --git a/frontend/app/hooks/useSearchBooks.ts b/frontend/app/hooks/useSearchBooks.ts
index 5802873f..29da52b2 100644
--- a/frontend/app/hooks/useSearchBooks.ts
+++ b/frontend/app/hooks/useSearchBooks.ts
@@ -14,17 +14,17 @@ const SEARCH_BOOKS: TypedDocumentNode<
 > = gql`
   query SearchBooks(
     $title: String
-    $fuzzy: Boolean
+    $fuzzy: Boolean! = false
     $genres: [String!]
     $language: String
     $bookFormat: String
     $minPages: Int
     $maxPages: Int
     $minRatings: Int
-    $sortBy: BookSortField
-    $sortDirection: SortDirection
-    $limit: Int
-    $offset: Int
+    $sortBy: BookSortField! = ID
+    $sortDirection: SortDirection! = ASC
+    $limit: Int!
+    $offset: Int!
   ) {
     searchBooks(
       title: $title
diff --git a/frontend/app/lib/constants.ts b/frontend/app/lib/constants.ts
index 93da2a52..6c90edf1 100644
--- a/frontend/app/lib/constants.ts
+++ b/frontend/app/lib/constants.ts
@@ -7,4 +7,18 @@ const BOOK_PAGE_LIMIT = 12;
 // The minimum number of ratings of books on the home page.
 const HOME_MIN_RATINGS = 10_000;
 
-export { MIN_PASSWORD_LENGTH, BOOK_PAGE_LIMIT, HOME_MIN_RATINGS };
+// Make sure these match the limits in backend/src/schema/books/resolvers/Query/searchBooks.ts
+const MAX_QUERY_LENGTH = 200;
+const MAX_GENRES = 15;
+
+// GraphQL Int is 32-bit, so the offset (page - 1) * BOOK_PAGE_LIMIT must stay below 2^31.
+const MAX_PAGE = Math.floor((2 ** 31 - 1) / BOOK_PAGE_LIMIT);
+
+export {
+  MIN_PASSWORD_LENGTH,
+  BOOK_PAGE_LIMIT,
+  HOME_MIN_RATINGS,
+  MAX_QUERY_LENGTH,
+  MAX_GENRES,
+  MAX_PAGE,
+};