diff --git a/src/config.ts b/src/config.ts
index cce1ce2..246bf5a 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -144,9 +144,25 @@ const Conf = {
   local(path: string): string {
     return mergePaths(Conf.localDomain, path);
   },
+  /** URL to send Sentry errors to. */
   get sentryDsn() {
     return Deno.env.get('SENTRY_DSN');
   },
+  /** SQLite settings. */
+  sqlite: {
+    /**
+     * Number of bytes to use for memory-mapped IO.
+     * https://www.sqlite.org/pragma.html#pragma_mmap_size
+     */
+    get mmapSize(): number {
+      const value = Deno.env.get('SQLITE_MMAP_SIZE');
+      if (value) {
+        return Number(value);
+      } else {
+        return 1024 * 1024 * 1024;
+      }
+    },
+  },
 };
 
 const optionalBooleanSchema = z
diff --git a/src/db.ts b/src/db.ts
index 43d7f04..58576e5 100644
--- a/src/db.ts
+++ b/src/db.ts
@@ -1,7 +1,7 @@
 import fs from 'node:fs/promises';
 import path from 'node:path';
 
-import { DenoSqlite3, DenoSqliteDialect, FileMigrationProvider, Kysely, Migrator } from '@/deps.ts';
+import { DenoSqlite3, DenoSqliteDialect, FileMigrationProvider, Kysely, Migrator, sql } from '@/deps.ts';
 import { Conf } from '@/config.ts';
 
 interface DittoDB {
@@ -55,12 +55,27 @@ interface UnattachedMediaRow {
   uploaded_at: Date;
 }
 
+const sqlite = new DenoSqlite3(Conf.dbPath);
+
+setPragmas(sqlite, {
+  synchronous: 'normal',
+  temp_store: 'memory',
+  mmap_size: Conf.sqlite.mmapSize,
+});
+
 const db = new Kysely<DittoDB>({
   dialect: new DenoSqliteDialect({
-    database: new DenoSqlite3(Conf.dbPath),
+    database: sqlite,
   }),
 });
 
+function setPragmas(db: DenoSqlite3, pragmas: Record<string, string | number>) {
+  for (const [pragma, value] of Object.entries(pragmas)) {
+    db.prepare(`PRAGMA ${pragma} = ${value}`).run();
+    console.log(`PRAGMA ${pragma} = ${db.prepare(`PRAGMA ${pragma}`).value()}`);
+  }
+}
+
 const migrator = new Migrator({
   db,
   provider: new FileMigrationProvider({