In gRPC, streaming is used when a simple request-response pattern (like in typical HTTP APIs) isn’t sufficient—usually due to performance, real-time data needs, or the nature of the communication. gRPC supports four types of communication:

• Unary RPC – Single request, single response

• Server-Side Streaming RPC – Single request, stream of responses

• Client-Side Streaming RPC – Stream of requests, single response

• Bidirectional Streaming RPC – Stream of requests, stream of responses

Here’s when to use each streaming type:

1. Unary RPC

Use when: You just need a simple request-response.

✅ Most common, lightweight, and easy to debug.

Example:

• Getting a user profile by ID

• Fetching a product detail page

rpc GetUserById(Request) returns (User);

2. Server-Side Streaming

Use when:

• You send a single request and expect multiple results over time.

• The client doesn’t need to send anything else after the first request.

Use cases:

• Logs/Events stream: Get logs from a server for a specific timeframe

• Search results pagination: Stream results as they’re found

• Large data export: Chunked file download or list of users

rpc ListUsers(Request) returns (stream User);

3. Client-Side Streaming

Use when:

• The client needs to send a sequence of data before getting a response.

• Great when batching requests or uploading chunks.

Use cases:

• Uploading files in chunks

• Sending multiple metrics or sensor data

• Batch create/update operations

rpc UploadMetrics(stream Metric) returns (Response);

4. Bidirectional Streaming

Use when:

• Both sides need to send a stream of messages independently.

• Useful for real-time, duplex communication.

Use cases:

• Chat applications

• Live gaming updates

• Real-time collaboration tools (e.g., Google Docs)

• IoT device communication with a central server

rpc Chat(stream Message) returns (stream Message);