What makes logs useful in production, and how do you avoid logging sensitive data?

Use structured logs without leaking sensitive data

Explains structured logging fields, safe context, redaction, event naming, and avoiding secret or personal-data leaks.

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TL;DR

I would use structured logs with consistent fields such as correlation id, route, status code, tenant id where safe, user id where safe, dependency name, duration, and error category. I would avoid logging raw passwords, tokens, API keys, reset links, full payment data, or large request bodies. The log explains the event and decision path without copying sensitive inputs forever.

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Structured fields, event names, log levels, redaction, PII, tokens, request bodies, and incident usefulness.

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Logs need to be searchable under pressure. Free-text dumps and secret-heavy logs both fail when an incident is happening.
I would use structured logs with consistent fields such as correlation id, route, status code, tenant id where safe, user id where safe, dependency name, duration, and error category. I would avoid logging raw passwords, tokens, API keys, reset links, full payment data, or large request bodies. The log explains the event and decision path without copying sensitive inputs forever.
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I would choose log levels deliberately. Normal request completion may be information or metrics-only, expected validation failures should not be error noise, and unexpected exceptions deserve error logs with stack trace and safe context. For business events, I would name events consistently so queries and dashboards are stable. Redaction should happen centrally for known sensitive headers and fields.

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Details

Logging raw Authorization headers or tokens.
Using only string interpolation with no structured fields.
Logging every expected validation failure as an error.
Dumping entire request bodies during incidents.

What makes logs useful in production, and how do you avoid logging sensitive data?

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