Prisma "Timed out fetching a new connection from the connection pool" in CI

Prisma keeps a bounded connection pool. When more concurrent queries are in flight than the pool allows, requests wait; if none frees up within the timeout, Prisma throws a pool timeout. Parallel CI tests hit this fast.

What this error means

Tests fail with "Timed out fetching a new connection from the connection pool. More info: ... (Current connection pool timeout: 10, connection limit: N)" under parallelism.

Timed out fetching a new connection from the connection pool. More info: https://pris.ly/d/connection-pool
(Current connection pool timeout: 10, connection limit: 5)

Common causes

Parallel work exceeds the pool size

A test runner executing many suites in parallel opens more concurrent queries than the connection_limit allows, so requests time out waiting.

Leaked or long-held connections

Long transactions or clients that are never disconnected hold connections, starving the pool for other queries.

How to fix it

Raise the connection limit or lower concurrency

1. Increase connection_limit in the URL, within the database max_connections.
2. Or reduce test worker parallelism so fewer queries run at once.
3. Reuse a single PrismaClient rather than one per test.

DATABASE_URL=postgresql://postgres:postgres@localhost:5432/app?connection_limit=15

Increase the pool timeout for bursts

Give the pool longer to hand out a connection when short bursts of concurrency are expected.

DATABASE_URL=postgresql://postgres:postgres@localhost:5432/app?connection_limit=10&pool_timeout=30

How to prevent it

• Size connection_limit to your CI concurrency and DB max_connections.
• Share one PrismaClient instance across tests.
• Disconnect clients and avoid long-held transactions.

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