Explain gRPC Streaming vs Unary Calls.
gRPC unary calls send one request and receive one response, while gRPC streaming allows continuous sending or receiving of multiple messages over a single connection.
When to Use
- Unary: Best for simple operations like login requests, fetching a profile, or one-off queries.
- Streaming: Ideal for real-time use cases like chat apps, stock tickers, IoT telemetry, or video streaming.
Example
A messaging app might use streaming to deliver a live chat feed, while fetching a user’s profile remains a unary call.
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Why Is It Important
Picking the right RPC type affects performance, scalability, and cost. Streaming avoids repeated handshakes, improving throughput, while unary calls keep services stateless and easier to scale.
Interview Tips
- Define both clearly.
- Give one real-world example for each.
- Mention efficiency, scalability, and error handling.
- Bonus: Highlight that gRPC uses HTTP/2 streams under the hood.
Trade-offs
-
Unary: Simpler, stateless, easy load-balancing.
-
Streaming: Higher throughput, less overhead, but adds complexity in error handling and state management.
Pitfalls
- Using streaming for simple tasks can add unnecessary complexity.
- Forgetting to close or cancel streams leads to resource leaks.
- Assuming streaming is always faster—sometimes unary performs better depending on workload.
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