perf: reuse the auth instance when the database is process-wide by onmax · Pull Request #659 · nuxt-modules/better-auth

onmax · 2026-10-26T05:23:50Z

With a NuxtHub database, serverAuth() builds a new Better Auth instance on every request, and it calls the app's defineServerAuth factory before checking the cache, so every plugin factory runs again too. Each SSR page hits this through the /api/auth/get-session call.

#295 made database-backed instances per-request because a Hyperdrive postgres client must not outlive a Worker request. That is the only request-scoped case: NuxtHub creates db once per process or isolate for its other drivers, D1 included.

This PR:

adds isRequestScopedDatabase(event) to #auth/database (true only when a Hyperdrive binding with a connection string is present);
caches the instance unless the database is request-scoped (the derived-secret rule is unchanged);
looks the cache up before calling createServerAuth(), so a cache hit skips the plugin factories.

serverAuth() is documented as a module-level singleton, so this brings database setups in line with the docs.

Repro

https://github.com/onmax/repros/tree/repro/better-auth-shared-db-cache/better-auth-shared-db-cache

git clone --branch repro/better-auth-shared-db-cache https://github.com/onmax/repros
cd repros && node verify.mjs

better-auth-shared-db-cache: 10 page requests -> defineServerAuth factory called 10 times (expected 10)
better-auth-shared-db-cache: serverAuth() returns the same instance on the next request: false (expected false)
better-auth-shared-db-cache-fix: 10 page requests -> defineServerAuth factory called 1 times (expected 1)
better-auth-shared-db-cache-fix: serverAuth() returns the same instance on the next request: true (expected true)

The -fix fixture applies this change as a pnpm patch to 0.3.13.

Effect

Production build of a Portal-shaped Nuxt 4.6.2 app (NuxtHub Postgres via postgres-js; jwt, mcp and cimd plugins). Server CPU per request, mean of 2 interleaved runs, identical HTML:

page	before	after
near-empty page	15.4 ms	9.7 ms (−37%)
form, ~40 fields	59.0 ms	53.1 ms (−10%)
guest `/` (`auth: { only: 'guest' }`)	34.4 ms	20.3 ms (−41%)

In the CPU profile, serverAuth took 2.0 ms of a 9.5 ms request: 1.6 ms in the plugin factories and 0.6 ms in betterAuth() (schema index resolution, drizzle introspection and diff).

Checks

test/server-auth-database-cache.test.ts: per-request tests now set isRequestScopedDatabase to true; a new test checks one instance and one factory call across requests with a process-wide adapter. The new test and the updated no-database test fail on main.
pnpm lint, pnpm typecheck, pnpm typecheck:runtime-server, pnpm test:runtime, and the server-auth vitest files pass locally.

🤖 Generated with Claude Code

vercel · 2026-10-26T05:23:55Z

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Project	Deployment	Actions	Updated
nuxt-better-auth-docs	Ready	Preview	Oct 26, 2026 5:40am UTC

vite-hub · 2026-10-26T05:23:56Z

Session	Status	Started	Duration
Pending	Completed	Not started	—

Latest result

Pull request merged.

Final answers

Session

Pull request merged.

Session

Waiting for GitHub merge request 9ae77912-9bf6-465c-bc08-1049f7fa54dc.

Session