Delivery semantics and reliability

Guarantee model

End-to-end message delivery guarantees are a combination of:

the selected PURISTA event bridge
broker/component configuration
your handler design (idempotency, retries, side effects)

Common modes

at-most-once: lower overhead, messages can be lost
at-least-once: safer delivery, duplicates are expected
exactly-once: rarely guaranteed end-to-end across distributed side effects

Design rules for production

make command/subscription side effects idempotent
use deterministic business keys for deduplication
avoid non-atomic “read/modify/write” side effects without protection
set timeout and retry budgets intentionally
persist important business state outside process memory

Streams and reliability

Current stream runtime support is available in DefaultEventBridge only.

For stream consumers:

handle terminal frames (complete, error, cancel) explicitly
treat cancellation as a normal control path
validate chunk/final payloads where needed
keep chunk processing resilient to partial interruptions

Minimal acceptance checklist

broker-level delivery mode is documented for each environment
duplicate-handling strategy is tested
retry policy is tested against transient failures
operational runbook includes outage and reconnect behavior