// Learning · 06

Communication & Integration

How services talk: calls, messages, gateways and meshes.

Review 10 flashcards→

1.REST / HTTP
Service Aleads toHTTP + JSONService B
Ask, then wait. Simple, universal, and blocked until it answers.
Open the diagram→
- Service A uses / calls Service B (1 GET /orders/42)
- Service B uses / calls Service A (2 200 + JSON)
- Service A fails / error path Timeout (no reply in 2s)
2.gRPC
Client stubleads toHTTP/2 + ProtobufServer
Typed contracts, binary payloads, streaming. Fast between services.
Open the diagram→
- inventory.proto creates Client stub (codegen)
- inventory.proto creates Inventory server (codegen)
- Client stub uses / calls Inventory server (1 GetStock)
- Inventory server publishes / notifies Client stub (2 stream updates)
3.GraphQL
Client queryleads toOne endpointleads toExactly the fields
The client asks for exactly the shape it needs, in one round trip.
Open the diagram→
- Web app uses / calls /graphql endpoint (1 query)
- Mobile app uses / calls /graphql endpoint (1 query)
- /graphql endpoint uses / calls Resolvers (2 resolve)
- Resolvers uses / calls Orders (fetch)
- Resolvers uses / calls Customers (fetch)
- Resolvers uses / calls Products (fetch)
4.Webhooks
Providerleads toHTTP POSTYour endpoint
Don't call us, we'll call you. An HTTP POST when something happens.
Open the diagram→
- Payment provider uses / calls Your endpoint (1 POST event)
- Your endpoint uses / calls Payment provider (2 200 OK)
- Your endpoint creates Message queue (3 enqueue)
- Message queue uses / calls Background worker (4 process)
5.Message Queue
Producerleads toQueueleads toOne consumer
Drop the work off and move on. One consumer picks up each message.
Open the diagram→
- Orders API creates Invoice queue (1 send)
- Invoice queue uses / calls Worker 1 (2 receive)
- Invoice queue uses / calls Worker 2 (2 receive)
- Invoice queue uses / calls Worker 3 (2 receive)
- Worker 3 fails / error path Dead-letter queue (after 5 tries)
6.Publish / Subscribe
Publisherleads toTopicleads toEvery subscriber
Announce it once. Everyone who cares gets their own copy.
Open the diagram→
- Orders service publishes / notifies OrderPlaced topic (1 publish)
- OrderPlaced topic publishes / notifies Billing (2 copy)
- OrderPlaced topic publishes / notifies Shipping (2 copy)
- OrderPlaced topic publishes / notifies Analytics (2 copy)
7.API Gateway
Clientleads toGatewayleads toServices
One front door. Auth, routing, and rate limits handled in one place.
Open the diagram→
- Client uses / calls API gateway (1 request)
- API gateway uses / calls Orders (2 /orders/**)
- API gateway uses / calls Catalog (2 /catalog/**)
- API gateway uses / calls Users (2 /users/**)
8.Backend for Frontend
Mobile / Webleads toOwn BFFleads toServices
Each client gets its own backend, shaped for its screens.
Open the diagram→
- Mobile app uses / calls Mobile BFF (1 GET /home)
- Web app uses / calls Web BFF (1 GET /dashboard)
- Mobile BFF uses / calls Profile (2 parallel)
- Mobile BFF uses / calls Orders
- Mobile BFF uses / calls Recommendations
- Web BFF uses / calls Profile
- Web BFF uses / calls Orders
9.Service Mesh
Svc Aleads tomTLSProxy → Proxyleads toSvc B
Retries, encryption, and routing pulled out of your code entirely.
Open the diagram→
- Orders uses / calls Orders proxy (1 request)
- Orders proxy uses / calls Inventory proxy (2 mTLS)
- Inventory proxy uses / calls Inventory (3 local call)
- Control plane uses / calls Orders proxy (push config)
- Control plane uses / calls Inventory proxy (push config)
10.Sidecar
Appleads tosame podHelper
A buddy container handling logs and config so the app stays clean.
Open the diagram→
- Orders app uses / calls Log shipper sidecar (localhost)
- Orders app creates Shared volume (1 write logs)
- Log shipper sidecar uses / calls Shared volume (2 read logs)
- Log shipper sidecar publishes / notifies Log backend (3 ship logs)
- Log shipper sidecar uses / calls Config store (read config)

1.REST / HTTP

2.gRPC

3.GraphQL

4.Webhooks

5.Message Queue

6.Publish / Subscribe

7.API Gateway

8.Backend for Frontend

9.Service Mesh

10.Sidecar