retryability

Retryability refers to the property of an operation or request that allows it to be safely retried after a failure, without causing unintended side effects or inconsistent state. In practice, retryability is closely linked with idempotence—the guarantee that performing the same operation multiple times yields the same result as performing it once. Operations that are inherently retryable are designed to be idempotent or to apply compensating actions if repeated.

In software systems, retryability is considered when interacting with networks, databases, and external services. Some operations are clearly retryable, such as reads or creating a resource with an idempotent key. Others are not, such as non-idempotent writes without safeguards, or actions that could violate business rules if executed twice. Systems often classify failures into transient (retryable) and permanent (not retryable) and apply different policies accordingly.

Retry policies commonly use exponential backoff with jitter, a maximum number of attempts, and per-error routing. Additional patterns optimize reliability, including circuit breakers to stop retrying during sustained failures, deduplication to prevent processing duplicates, and the use of idempotency keys or compensating transactions for non-idempotent operations.

Designing for retryability also involves observability and testing: monitoring retry rates, success rates, and latency; simulating outages; and ensuring that retries do not exhaust resources or cause cascading failures. When implemented carefully, retryability improves resilience and fault tolerance but requires clear guarantees about state and side effects to avoid data corruption or user-visible inconsistencies.