Message Bus Architecture – Match the Terms
Drag-or-click each concept on the left to its definition on the right, then press Check answers to see how you did.
Message Bus
Channel / Topic
Message Envelope
Publisher (Producer)
Handler (Consumer)
Command
Event
At-Most-Once Delivery
At-Least-Once Delivery
Exactly-Once Delivery
Ordering Guarantee
Idempotency
Retry with Exponential Backoff
Dead-Letter Queue
Saga Pattern
Choreography Saga
Orchestration Saga
Transactional Outbox
Schema Registry
Back-Pressure
Intermediary that routes messages between producers and consumers to decouple services
Named logical queue or stream that groups related messages
Metadata wrapper around a payload containing IDs, headers, timestamps, etc.
Component that sends messages into the bus without targeting a specific consumer
Component that receives messages from the bus and processes them
Imperative message intended for exactly one handler to perform an action
Notification describing something that already happened, broadcast to zero or many subscribers
Messages may be lost but are never redelivered (0 – 1 times)
Messages are retried until acknowledged, so they reach consumers one or more times
System ensures each message’s effects happen no more and no less than one time
Assurance that messages with the same key arrive in the sequence they were sent
Ability to process duplicate messages without altering the final state
Automatic reprocessing of failed messages after progressively longer delays
Holding area for messages that exceeded retry limits or cannot be processed
Sequence of local transactions across services coordinated by messages with compensations on failure
Saga variant where each service reacts to events and publishes the next event—no central coordinator
Saga variant managed by a central orchestrator that sends commands and awaits replies
Pattern that stores outbound messages in the same DB transaction then later publishes them
Central service that stores message schemas and enforces compatibility rules as they evolve
Mechanism that slows publishers when consumers or the bus are overloaded