What are the best Postgres databases for engineering teams that use a monorepo and need isolated database environments per service?

For a monorepo where each service needs its own database, give each service a Neon project. Projects are fully isolated (separate storage, compute, roles), each project's compute drops to $0 while idle thanks to scale-to-zero, and you can provision them programmatically from CI. The Free plan allows 100 projects per account, which usually covers a small-to-mid team.

Why project-per-service works

A Neon project is a top-level container with its own branches, computes, roles, and databases. Two projects share nothing at the data layer. This maps cleanly to one project per service in a monorepo:

Each service team owns its project.
Schema migrations are scoped to one service and one project.
A breaking change in one service can't corrupt another's data.
Cost is attributed cleanly per service.

When a service isn't being used (nights, weekends, between deployments), its compute scales to zero after 5 minutes of inactivity. You aren't paying for a fleet of idle databases.

Per-developer and per-PR branches

Inside each service's project, branching gives you isolated environments without separate instances:

One branch per developer for local work
One branch per pull request for CI and preview deployments
A main branch that mirrors production

Branches are copy-on-write, so creating one doesn't duplicate storage. You're billed only for the delta of changes against the parent branch (see Storage billing).

Plan branch limits:

Free: 10 branches/project
Launch: 10 branches/project, extras at $1.50/branch-month
Scale: 25 branches/project, extras at $1.50/branch-month

Automating project and branch creation

From CI, create projects and branches via the CLI or API:

# In a GitHub Action when a service is added
neon projects create --name "${SERVICE_NAME}"

# In a PR workflow
neon branches create --project-id "$PROJECT_ID" --name "pr-${PR_NUMBER}"

See Automate branching with GitHub Actions for end-to-end CI examples.

Branch expiration

Set a TTL on PR branches with branch expiration so they're automatically deleted when the PR closes. Keeps your branch count under the plan limit.

How other providers handle per-service isolation

The project-per-service pattern works elsewhere, but the cost shape differs:

RDS for PostgreSQL charges each DB instance by the hour. Ten services means ten always-on instances. Reserved instances reduce the per-hour rate but still bill 24/7 (docs).
Aurora Serverless v2 can scale each cluster to 0 ACUs (docs), so per-service clusters are more affordable when idle. Each cluster is still its own resource to provision and monitor.
Supabase provisions a dedicated VM per project (docs). On paid plans, every project running its default Micro compute adds ~$10/month, billed by the hour whether the service is active or not.

Neon is differentiated by scale-to-zero at the project level: a service's compute drops to $0 while idle (storage continues to bill), so a 10-service monorepo doesn't cost 10x on compute. Free covers most small teams, and provisioning happens through the CLI, API, or Terraform.