Kafka

Synchronous HTTP calls create tight coupling. Service A waits for Service B, which waits for Service C. One slow service blocks everything. One failure cascades everywhere. Event-driven architecture breaks this chain. The Core Idea Instead of direct calls, services communicate through events: T O E O I S E r r v r n h m a d e d v i a d e n e e p i i r t r n p l t - t i i S d S o n S o e r e r g e n r i r y r a v v v S v l i e i S e i c n c e r c ( e e r v e s ( v i y → ← a → i c n s c e c H w y p e h T a n u r T i c b ← ← ← o P t h l n r i s s s o → ← o s u u u u n h b b b s I o e s s s ) n u s c c c : v s r r r e ) " i i i n : O b b b t r e e e o d s s s r e y r ← ← ← C S r " " " e e O O O r a r r r v t d d d i e e e e c d r r r e " C C C r r r → ← → e e e a a a H w M t t t T a e e e e T i s d d d P t s ↓ " " " a → ← g e S h B i r p o p k i e n r g S e r v i c e The Order Service doesn’t know or care who’s listening. It just announces what happened. ...

Request-response is synchronous. Events are not. That difference changes everything about how you build systems. In event-driven architecture, components communicate by producing and consuming events rather than calling each other directly. The producer doesn’t know who’s listening. The consumer doesn’t know who produced. This decoupling enables scale, resilience, and evolution that tight coupling can’t match. Why Events? Temporal decoupling: Producer and consumer don’t need to be online simultaneously. The order service publishes “OrderPlaced”; the shipping service processes it when ready. ...