Logs are essential for debugging.
But logs can become a problem when developers treat them like a permanent database.
An application log should help you understand what happened—not become a storage system for everything your users do.
What Belongs in Logs?
Useful information might include:
Request started Payment request failed Database connection error User authentication failed Deployment completed
The exact information depends on the application.
Be Careful With Sensitive Data
Avoid logging things such as:
Passwords API keys Access tokens Full payment information Private user data
A log file can be accessible to more people and systems than you expect.
If sensitive information is written into logs, you've potentially created another place that needs to be protected.
Logs Should Be Searchable
When something goes wrong, you want to answer:
What happened?
Good logs should provide enough context to trace an issue.
For example:
2026-09-10 10:32 Payment request failed Order: 48392 Provider: example Error: timeout
That's much more useful than:
Something failed. Don't Log Everything
More logs don't automatically mean better debugging.
Too much noise makes important errors harder to find.
Log events that help explain application behavior.
Think About Retention
Logs consume storage.
Keeping everything forever isn't always necessary.
Decide how long logs should remain available based on your operational and compliance requirements.
Good Logs Save Time
When production breaks, good logs can turn:
“Something is wrong.”
into:
“The payment API started timing out at 10:32.”
That difference can save hours.
Logs are for understanding your system. Design them accordingly.