Event-Driven Architecture Requirement Diagram Template

A requirement diagram for event-driven architecture (EDA) captures the functional and non-functional requirements governing how producers emit events, how brokers route and persist them, and how consumers process them. This template structures those relationships visually, making it easy to trace which system components must satisfy specific throughput, reliability, or ordering constraints. Rather than leaving requirements scattered across documents, the diagram centralizes them so every stakeholder — from developers to product owners — can see dependencies at a glance.

## When to Use This Template

Reach for this template early in the design phase, before implementation begins. It is especially valuable when your EDA spans multiple teams or services, because it forces explicit agreement on broker guarantees (at-least-once vs. exactly-once delivery), consumer group isolation, and producer schema contracts. Use it again during architecture reviews or when onboarding new engineers who need to understand why certain constraints exist, not just what the system does.

## Common Mistakes to Avoid

One frequent error is conflating system design diagrams with requirement diagrams. A requirement diagram should state *what* the system must do — for example, "The broker MUST deliver events within 500 ms under peak load" — not *how* it achieves that. Another mistake is omitting traceability links: every requirement node should connect back to a business goal or a consumer/producer component, otherwise the diagram becomes an orphaned list. Teams also tend to under-specify broker requirements, focusing only on producers and consumers, which leads to ambiguous SLA ownership when incidents occur. Finally, avoid cramming implementation details such as topic names or partition counts into requirement nodes; those belong in a separate architecture or deployment diagram. Keeping the requirement diagram clean and constraint-focused ensures it remains a living document that guides decisions throughout the project lifecycle.