Reduce Lambda Cold Starts with Provisioned Concurrency
Set provisioned concurrency on the alias so the first N invocations have no init delay and p99 latency drops.
Task
Configure aws lambda put-provisioned-concurrency --function-name api --qualifier prod --provisioned-concurrent-executions 10 so the cloud resource enforces the control automatically without manual console steps.
When to use this
An audit finds that aws lambda put-provisioned-concurrency --function-name api --qualifier prod --provisioned-concurrent-executions 10 was configured manually and drifted, leaving a resource exposed for two weeks.
Prerequisites
- Terraform or IaC tooling installed
- Cloud provider credentials with target permissions
Steps
1. Configure aws lambda put-provisioned-concurrency --function-name api --qualifier prod --provisioned-concurrent-executions 10 in the project configuration file with the recommended defaults.
aws lambda put-provisioned-concurrency --function-name api --qualifier prod --provisioned-concurrent-executions 10
Expected output: The configuration is accepted and aws lambda put-provisioned-concurrency --function-name api --qualifier prod --provisioned-concurrent-executions 10 runs without errors on the first invocation.
2. Run the check locally to verify aws lambda put-provisioned-concurrency --function-name api --qualifier prod --provisioned-concurrent-executions 10 produces the expected result before pushing.
pnpm test
Expected output: Local run matches CI behavior; no surprises after push.
3. Add the gate to the CI pipeline so aws lambda put-provisioned-concurrency --function-name api --qualifier prod --provisioned-concurrent-executions 10 blocks merge on failure.
- name: Run add lambda cold start provision
run: pnpm test
Expected output: Pull requests with failing aws lambda put-provisioned-concurrency --function-name api --qualifier prod --provisioned-concurrent-executions 10 are blocked from merging.
Troubleshooting
Problem
The check passes locally but fails in CI
Solution
Pin dependency versions and the runtime to match CI exactly; reproduce with the same Docker image or act.
Problem
Configuration is rejected with a schema error
Solution
Check the tool version matches the config schema; older versions may not support newer fields.
Limitations
- The gate only runs on events that trigger the workflow; locally pushed commits bypass it.
- Configuration drift is possible if someone edits settings outside version control.
Codify the control
Start by measuring the problem. Set provisioned concurrency on the alias so the first N invocations have no init delay and p99 latency drops. The most common mistake is adding the gate without first confirming it catches the issue you care about. Run aws lambda put-provisioned-concurrency –function-name api –qualifier prod –provisioned-concurrent-executions 10 against the current codebase and inspect the output before wiring it into CI.
aws lambda put-provisioned-concurrency --function-name api --qualifier prod --provisioned-concurrent-executions 10Detect drift
Once the gate is in place, make failures actionable. A failing aws lambda put-provisioned-concurrency –function-name api –qualifier prod –provisioned-concurrent-executions 10 should point to the exact file and line, not a generic error. Pin the tool version in the lockfile so a upstream release does not silently change behavior. Review the gate output in every pull request just like a test result.