deployment and operations

Logs

Logs explain what an application and runtime did. Useful logs are structured enough to search, correlated across a request or job, and careful not to leak secrets or unnecessary personal data. Logging everything is not the goal; the goal is to make failures diagnosable without creating another data leak.

Log request, job, or correlation IDs.
Use severity levels consistently.
Keep secrets, tokens, and passwords out of logs.

Trigger A Known Failure

Send logs to an operator-visible destination.
Trigger known failures.
Verify retention and access controls.

Keep Sensitive Data Out

Silent failures are hard to operate.
Verbose logs can become a data leak.
Local files disappear in disposable runtimes.

Structured Log Shape

{
  "level": "error",
  "message": "payment gateway timeout",
  "request_id": "req_01J...",
  "order_id": 9001,
  "secret": "never log this field"
}

Verify where logs go in the real runtime. Local files may disappear with disposable containers, and a log collector is useless if the team cannot search it or does not know the retention policy. Test one controlled failure in staging and trace it from the user-visible error to the relevant events.

Practice

Practice: Design A Logging Checklist

Design the minimum useful logging for a checkout request that calls a payment provider and dispatches a receipt job. Identify fields that must never be logged.

Requirements

Log request, job, or correlation IDs.
Use severity levels consistently.
Keep secrets, tokens, and passwords out of logs.
Send logs to an operator-visible destination.
Trigger known failures.
Verify retention and access controls.

Show solution

Generate a request or correlation ID at the boundary and carry it into payment and receipt-job logs. Include useful business identifiers such as an order ID, a severity level, and a concise event message.

Never log passwords, session IDs, access tokens, secret keys, or full payment details. Send staging logs to the operator-visible destination, trigger a controlled payment failure, and confirm that the request can be traced without exposing sensitive values.