Nonretryability

Nonretryability is a classification of certain failures in computing systems in which repeating the operation is unlikely to succeed or could cause harm. It distinguishes permanent or irrecoverable conditions from transient or intermittent errors that may be resolved by retrying.

Common causes include invalid or missing input, authentication or authorization failures, requests for nonexistent or irrecoverable resources, violations of business rules, and irreversible actions or data-loss risks. In many contexts, errors arising from client mistakes or policy blocks are treated as nonretryable.

In practice, services expose nonretryable errors via explicit error codes or messages, and clients are advised not to retry these errors automatically. Backend systems may route such tasks to dead-letter queues, log detailed telemetry, or trigger human review, while retry logic is reserved for retryable conditions such as transient network failures or temporary service outages. When appropriate, idempotent design helps prevent duplicate effects if retries occur accidentally.

Design considerations include documenting nonretryable conditions clearly, ensuring operations affecting state are idempotent where feasible, and providing clear guidance for clients on how to handle these errors. Effective telemetry and standardized error codes facilitate correct client behavior and faster diagnosis. In distributed systems, a nonretryable designation helps avoid wasted resources and maintains data integrity by preventing duplicated actions.

Examples commonly cited as nonretryable include HTTP 400 Bad Request due to invalid input, 401 or 403 for access issues, 404 for missing resources, or 422 Unprocessable Entity; business-rule violations and irreversible operations are also typically treated as nonretryable.