Solution / Application communication
Application-to-Application Signals for Lightweight Coordination
Move small authenticated signals between applications without turning the integration into a streaming platform.
Solution pattern; current signal foundationA focused communication contract
Applications often need to request a configuration refresh, announce available work, trigger synchronization or pass a small state-change signal. A pending mailbox can decouple sender timing from receiver availability.
Use it for small coordination messages
Keep the payload bounded and application-defined. The sender creates the signal with an idempotency key. The target reads pending records through authenticated polling, performs its business action and sends ACK.
What it is not
This pattern is not a replacement for Kafka, a bulk transfer system, a stream processor or an exactly-once workflow engine. Duplicate-safe business handling remains the receiver's responsibility.
Security and ownership
The current HMAC contract keeps secrets out of the request body, authenticates application scope and binds ACK authorization to the target application and tenant. Keep secrets server-side and redact them from logs.
Read the signal relay contract