Python Error Handling — Middle¶

Translate failures at boundaries. A database error should not leak directly into an HTTP response or a domain use case.

• Define a small domain exception hierarchy when callers need distinct recovery.
• Preserve the original cause with raise ... from exc.
• Validate untrusted input at the boundary.
• Log a failure once, where enough context exists to act.

Use retries only for known transient failures, with timeout, backoff, and idempotency.