What does it mean for a service to be production ready?

Checklist

Incomplete, but good enough I suppose.

Security

• Is authentication in place?
• Is authorization in place?
• Is rate limiting set up?

Testing

• Is the code covered by a reasonable amount of tests?
• Is a code style checker in place?
• Is a linter in place?
• Are tests run automatically?

Documentation

• Is the API documented? Is the authentication method documented?
• Is there a README? See How to write a good README for a product.
• Is there a template for PRs/MRs and for issues? See Pull request template.

Monitoring

• Is logging set up? (Ideally structured logging)
• Is instrumentation set up?

Good metrics to have:

• incoming requests (rate + latency)
• outgoing requests (rate + latency)
• queue size

Deployment

• Is deployment automated?
• Are there health and/or readiness endpoints?

Databases

• Are schema changes (migrations) automated?
• Are the right table indexes in place?