REST vs GraphQL vs gRPC

Choosing APIs for a food-delivery app

• Imagine designing a food-delivery app in a system design interview.
• REST, GraphQL, and gRPC suit different communication needs and can work together in the same system.

REST: simple resource operations

• Start with REST for the Orders screen:
  • Use GET to fetch order details.
  • Use POST to create a new order.
• Different screens may need different related data:
  • Orders List: restaurant details, order status, and billing information.
  • Order Details: order items, delivery address, and rider details.

GraphQL: flexible frontend data fetching

• GraphQL can be a good fit when different screens need different data from related database tables.
• Each screen selects only the fields it needs from the schema in a single query.
• The server collects the related data and sends it back to the frontend.
• Benefits:
  • The frontend only needs to send a single request.
  • The response does not contain unnecessary fields.
• Tradeoff: you need to maintain the GraphQL schema and server-side data-fetching logic.

gRPC: communication between backend services

• The backend has multiple services:
  • Order Service.
  • Payment Service.
  • Delivery Service, which assigns riders to orders.
• Consider gRPC for communication between these services:
  • Calling code can be automatically generated from the request-response contract, reducing manual integration work.
  • Protocol Buffers serialize messages into a compact binary format, reducing data size and potentially lowering latency.

Takeaway

• REST: simple resource operations.
• GraphQL: flexible data fetching on the frontend.
• gRPC: strongly typed communication between backend services.
• All three can work together in the same system.