Memory

Use Memory for throwaway development and tests, not production authentication. This complete Worker example keeps records only for the lifetime of each isolate.

Install

bun add @alchemy.run/better-auth better-auth@^1.7.5

No optional database driver or kysely peer is required by the memory adapter.

Define the database layer

src/auth-database.ts

import { Memory } from "@alchemy.run/better-auth/Memory";

export const AuthDatabase = Memory();

Construct the layer once for the host, not inside fetch, so requests in the same isolate share its store.

Define the auth Worker

src/worker.ts

import { BetterAuth } from "@alchemy.run/better-auth";
import * as Cloudflare from "alchemy/Cloudflare";
import * as Effect from "effect/Effect";
import { AuthDatabase } from "./auth-database.ts";

export default class AuthApi extends Cloudflare.Worker<AuthApi>()(
  "AuthApi",
  {
    main: import.meta.url,
    compatibility: { flags: ["nodejs_compat"] },
  },
  Effect.gen(function* () {
    const auth = yield* BetterAuth({
      basePath: "/api/auth",
      emailAndPassword: { enabled: true },
      migrate: false,
    });
    return { fetch: auth.fetch };
  }).pipe(Effect.provide(AuthDatabase)),
) {}

Better Auth instances remain request-scoped, while the layer retains the backing records across requests. Separate Worker isolates or Lambda instances never share these records.

Define the stack

alchemy.run.ts

import * as Alchemy from "alchemy";
import * as Cloudflare from "alchemy/Cloudflare";
import * as Effect from "effect/Effect";
import AuthApi from "./src/worker.ts";

export default Alchemy.Stack(
  "BetterAuthMemory",
  {
    providers: Cloudflare.providers(),
    state: Alchemy.localState(),
  },
  Effect.gen(function* () {
    const api = yield* AuthApi;
    return { url: api.url.as<string>() };
  }),
);

Alchemy generates and binds a stable signing secret, persisted in local stack state. That secret does not make the memory store persistent.

Run locally

bunx alchemy dev

Use the printed URL rather than assuming a local port. Set AUTH_ORIGIN to that URL to check the auth endpoint:

curl -i "$AUTH_ORIGIN/api/auth/get-session"

A restart or isolate replacement loses users and sessions. Even without a restart, a deployed request routed to a different isolate may not find a previously created user.

Inspect records in tests

When an in-process test needs access to the backing store, replace src/auth-database.ts with this file:

src/auth-database.ts

import { Memory } from "@alchemy.run/better-auth/Memory";
import type { MemoryDB } from "better-auth/adapters/memory";

export const records: MemoryDB = {};
export const AuthDatabase = Memory(records);

The adapter initializes missing model arrays from the auth schema, including plugins. Give independent tests independent stores; importing this module in the test process does not expose a separate Worker’s in-memory records.

Migration behavior

Memory has no migration support and needs no schema command. Leave migrate unset or false; explicitly setting it to true fails rather than pretending to migrate.

Choose D1 or another durable database before serving real users. See configuration, migrations, and the Memory reference.