TL;DR 🧠
REST is not always the best fit.
▪️ Need low-latency calls between services? → RPC
▪️ Need flexible data queries? → GraphQL
▪️ Need async, decoupled workflows? → Event/Messaging
Choose based on coupling, data needs, and runtime constraints — not hype. 🚀
🔸 REMOTE PROCEDURE CALL (RPC) 🛰
RPC = "call a function on another service as if it were local."
▪️ Typical stack: gRPC + protobuf
▪️ Fast, binary, low overhead 🔥
▪️ Strong contracts between services (IDLs / protobuf schemas)
▪️ Great for internal microservices talking to each other in real time
But…
▪️ Tight coupling between client and server interface
▪️ Harder across teams/orgs if you break compatibility
▪️ Not ideal for public/open APIs (tooling less universal than REST/HTTP+JSON)
When to use ✅
▪️ High-performance service-to-service calls inside your platform
▪️ You control both sides (same company, same versioning strategy)
🔸 GRAPHQL 🧬
GraphQL = "the client decides the shape of the response."
▪️ One endpoint, many query shapes
▪️ Ask only for what you need → less over/under-fetching 📦
▪️ Strongly typed schema = great DX for frontend
▪️ Can compose data from multiple backends in one request (BFF pattern)
But…
▪️ Can hide expensive queries behind “one request” (n+1 if not careful)
▪️ Caching is trickier than REST
▪️ Authorization rules can get complex per-field 🔐
When to use ✅
▪️ Public/partner/mobile/web APIs where consumers need flexibility
▪️ Aggregating multiple microservices into one client-facing API
🔸 MESSAGING / EVENT-DRIVEN API 📩
Event API = "don’t call me, I’ll tell you when something happens."
▪️ Producer publishes events (order.created, user.updated…)
▪️ Consumers react asynchronously
▪️ Loose coupling: producers don’t need to know who is listening 🙈
▪️ Scales naturally with new features (just add new consumers)
▪️ Great for audit, analytics, async workflows, integrations, CQRS, etc. 📊
But…
▪️ Harder mental model vs request/response
▪️ Delivery semantics, retries, idempotency, ordering… you need discipline
▪️ Debugging distributed flows can be harder
When to use ✅
▪️ Business events that trigger other processes (send email, update stock, bill customer)
▪️ Systems that must react in near real-time but not block the main request path
🔸 HOW DO I CHOOSE? 🤔
▪️ You’re in a microservices backend and you need speed → RPC
▪️ You’re building a public app/portal/mobile API → GraphQL
▪️ You’re building workflows/business reactions → Event/Messaging
➡️ You can (and often should) mix them in the same architecture. 💡
🔸 TAKEAWAYS 🏁
▪️ REST is a good default, but not the only tool
▪️ RPC = performance + control
▪️ GraphQL = flexibility + client power
▪️ Event API = decoupling + scalability
▪️ Picking the wrong style hurts long-term more than it hurts day 1 🧩
#api #rest #rpc #graphql #eventdriven #microservices #architecture
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