Getting Started with gRPC and Spring Boot — A Beginner’s Guide

As microservices become the backbone of modern backend architecture, efficient communication between services becomes more critical. In this post, we’ll explore how gRPC fits into the picture and how you can get started with it using Spring Boot.

🧠 What is gRPC and Why Use It?

gRPC is a modern, open-source, high-performance Remote Procedure Call (RPC) framework created by Google.

But what does that mean in simple words?

• Imagine calling a method of a class that’s located in a different server or system — that’s what gRPC lets you do.

🟢 Key Features of gRPC:

• Uses Protocol Buffers (Protobuf) — a fast and compact data format

• Supports multiple programming languages (Java, Go, Python, etc.)

• Enables contract-first development using .proto files

• Offers streaming (server, client, and bi-directional)

• Built-in support for authentication, load balancing, and deadlines

🔄 gRPC vs REST — What’s the Difference?

✅ Use REST when you're building open/public APIs.
🚀 Use gRPC for internal communication between microservices where performance matters.

🧰 How Spring Boot Supports gRPC

Out of the box, Spring Boot doesn’t have native gRPC support, but the community provides great libraries like:

• yidongnan/grpc-spring-boot-starter – most popular starter library

• LogNet/grpc-spring-boot-starter – another alternative

These libraries let you:

• Create gRPC services using @GRpcService

• Register interceptors

• Inject Spring-managed beans into gRPC services

• Easily manage service discovery, security, and observability

🔍 When to Use gRPC?

1️⃣ You Need Low Latency, High Throughput Communication

Use Case: Financial trading platforms, ad bidding systems
Example: A trading engine uses gRPC to execute millions of trades per second with sub-ms latency.

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2️⃣ You’re Working with Polyglot Microservices

Use Case: Cross-language service communication
Example: A Python-based ML model communicates with a Java order service via gRPC using Protobuf contracts.

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3️⃣ You Want Real-Time Communication

Use Case: Chat, live dashboards, game backends, telemetry
Example: A ride-sharing app streams driver location updates to the user’s device using server-streaming gRPC.

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4️⃣ You Need Full-Duplex Streaming (Bi-directional)

Use Case: Video conferencing, collaborative editing, WebRTC control channels
Example: A video conferencing tool uses gRPC for signaling between peers and real-time session sync.

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5️⃣ You Prefer Strongly Typed APIs with Contract-First Design

Use Case: Large-scale enterprise APIs with strict schema validation
Example: A bank’s internal APIs use .proto contracts to enforce strict structure across all services and languages.

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6️⃣ You’re Building a Service Mesh or Internal Platform

Use Case: Secure, observable internal comms in a Kubernetes cluster
Example: With Istio, gRPC traffic between services is encrypted and tracked with tracing headers like Zipkin/Jaeger.

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7️⃣ You Need Built-in Support for Deadlines, Retries & Flow Control

Use Case: Payment gateways, fraud detection services
Example: A payment microservice sets deadlines (e.g. 300ms) for downstream calls to avoid cascading timeouts during peak load.

🚫 gRPC Anti-Patterns & When Not to Use It

1️⃣ Replacing REST Everywhere

❌ Anti-pattern: Migrating all REST APIs to gRPC just because it's "faster"
💡 Why avoid: gRPC is optimized for internal, low-latency services — not public APIs. Browsers don't support gRPC natively (without gRPC-Web), making REST a better choice for external consumers.

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2️⃣ Using gRPC for CRUD-heavy APIs

❌ Anti-pattern: Rewriting simple CRUD endpoints in gRPC
💡 Why avoid: REST fits better for resource-oriented operations. gRPC adds unnecessary complexity for basic GET/POST/PUT/DELETE logic.

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3️⃣ Ignoring Protocol Compatibility

❌ Anti-pattern: Changing .proto definitions without versioning
💡 Why avoid: gRPC doesn't handle breaking changes well. Clients can break without backward compatibility plans.

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4️⃣ Too Many Microservices with Tight Coupling

❌ Anti-pattern: Overusing gRPC to connect microservices that constantly call each other
💡 Why avoid: High coupling over gRPC leads to latency chains and fragile systems. Consider async or event-driven alternatives.

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5️⃣ Exposing gRPC APIs Directly to Web/JS Clients

❌ Anti-pattern: Serving gRPC to browsers without gRPC-Web
💡 Why avoid: Browsers can’t consume native gRPC due to HTTP/2 & binary encoding. gRPC-Web or a REST gateway is needed.

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6️⃣ Skipping Timeouts and Deadlines

❌ Anti-pattern: Not configuring .withDeadline() on gRPC calls
💡 Why avoid: This can lead to stuck requests, resource leaks, or cascading failures under load.

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7️⃣ Forgetting Monitoring/Tracing

❌ Anti-pattern: No observability on gRPC streams or RPC failures
💡 Why avoid: Debugging gRPC issues without metrics, logs, or traces is painful. Use tools like OpenTelemetry, Zipkin, or Prometheus.

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8️⃣ Using gRPC for Long-Lived Connections (e.g. polling-like use cases)

❌ Anti-pattern: Replacing WebSocket-like needs with client-side polling over gRPC
💡 Why avoid: This misuses gRPC’s strengths. Consider proper pub-sub or push mechanisms.

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9️⃣ Ignoring Backward Compatibility in Streaming

❌ Anti-pattern: Changing message structure in streaming APIs without schema evolution
💡 Why avoid: Streaming clients may fail midway. Always evolve messages safely.

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🔟 Using gRPC in Teams Not Ready for It

❌ Anti-pattern: Adopting gRPC without team familiarity with Protobuf, tooling, or streaming
💡 Why avoid: It increases ramp-up time and dev friction. REST may be better until the team is comfortable.

🛠️ Quick Setup: Your First gRPC Project 
    with Spring Boot (Maven Edition)

1️⃣ Create a New Spring Boot Project

---

Use Spring Initializr:

• Project: grpc-hello-springboot

• Language: Java 11

🧪 Project layout

• grpc-hello-springboot/
  ├── pom.xml
  ├── src/
  │   └── main/
  │       ├── java/com/example/grpc/
  │       │   ├── GrpcApplication.java
  │       │   ├── GreeterService.java
  │       │   ├── GreeterClient.java
  │       │   └── GreeterController.java
  │       └── proto/greeter.proto
  └── src/main/resources/
      └── application.properties

2️⃣ quick explanation of each class and its responsibility in the grpc-hello-springboot project:

---

📁 GrpcApplication.java

Role: Application bootstrapper
Responsibility:

• Entry point for the Spring Boot application (main() method).

• Triggers component scanning and starts the embedded Tomcat + gRPC server.

📁 GreeterService.java

Role: gRPC server-side service implementation
Responsibility:

• Implements the GreeterGrpc.GreeterImplBase class generated from greeter.proto.

• Handles gRPC requests on the server (sayHello() method).

• Annotated with @GrpcService to register it as a gRPC service.

📁 GreeterClient.java

Role: gRPC client stub wrapper
Responsibility:

• Builds and manages the gRPC client connection to the gRPC server (localhost:9090).

• Provides a method sayHello(String name) that sends a gRPC request to the server.

📁 GreeterController.java

Role: REST controller (Spring MVC)
Responsibility:

• Exposes a REST endpoint at /api/greet?name=....

• Calls the gRPC client internally to forward the request and return the gRPC server's response.

📁 greeter.proto

Role: Protocol buffer contract
Responsibility:

• Defines the gRPC service interface (Greeter) and message types (HelloRequest, HelloResponse).

• Used to generate Java classes for both server and client communication.

📁 application.properties

Role: Configuration
Responsibility:

• Configures ports:

  • grpc.server.port=9090 → gRPC server

  • server.port=8080 → REST API

• Can include other Spring or gRPC settings as needed.

3️⃣ Detailed explanation of greeter.proto

---

• syntax = "proto3";
  option java_multiple_files = true;
  option java_package = "com.example.grpc";
  option java_outer_classname = "GreeterProto";
  
  service Greeter {
    rpc SayHello (HelloRequest) returns (HelloResponse);
  }
  message HelloRequest {
    string name = 1;
  }
  message HelloResponse {
    string message = 1;
  

🧩 Generated Message Classes

🔌 Generated Service Class (Stub)

📊 GreeterGrpc – Inside This Class

🔁 Streaming Types in gRPC

4️⃣ Server - Side Example:

---

• 
  @GrpcService
  public class GreeterService extends GreeterGrpc.GreeterImplBase {
      @Override
      public void sayHello(HelloRequest req, StreamObserver<HelloResponse> responseObserver) {
          String message = "Hello, " + req.getName();
          HelloResponse response = HelloResponse.newBuilder()
                                                .setMessage(message)
                                                .build();
          responseObserver.onNext(response);
          responseObserver.onCompleted();
      }
  }

5️⃣ Client - Side Example:

---

• 
  @Service
  public class GreeterClient {
  
      private final GreeterGrpc.GreeterBlockingStub stub;
  
      public GreeterClient() {
          ManagedChannel channel = ManagedChannelBuilder
                                    .forAddress("localhost", 9090)
                                    .usePlaintext()
                                    .build();
          stub = GreeterGrpc.newBlockingStub(channel);
      }
  
      public String sayHello(String name) {
          HelloRequest request = HelloRequest.newBuilder().setName(name).build();
          HelloResponse response = stub.sayHello(request);
          return response.getMessage();
      }
  } 

6️⃣ Summary:

---

• GET /api/greet?name=Viral hits the REST controller.

• Controller calls GreeterClient.sayHello(name)

• GreeterClient makes a gRPC request to GreeterService via the blocking stub.

• The server returns a gRPC response (HelloResponse) which is transformed into a REST response.

✅Code Repository Link 

• springboot_gRpc

🧭 REST → gRPC Call Flow Diagram

• ┌──────────────────────┐
  │  REST Client (e.g.                           │
  │  Postman, browser)                        │
  └──────────┬───────────┘
                              │
                             ▼
   ┌─────────────────────┐
   │ Spring Boot                                  │
   │ REST Controller                           │
   │ `GreeterController                        │
   └──────────┬──────────┘
                               │ Calls
                              ▼
   ┌──────────────────────┐
   │ gRPC Client Stub                            │
   │ `GreeterClient`                                │
   │ Uses Blocking Stub                         │
   └──────────┬───────────┘
                               │
                              ▼
   ┌─────────────────────┐
   │ gRPC Server                                │
   │ `GreeterService`                           │
   │ extends GreeterImpl                     │
   └──────────┬──────────┘
                               │
                              ▼
   ┌─────────────────────┐
   │ Business Logic                             │
   │ Create gRPC Response               │
   └──────────┬──────────┘
                               │
                              ▼
      Response sent backas RES

🚀 What’s Next?

Now that you’ve built your first gRPC-based Spring Boot app and seen it in action, it’s time to go deeper.

In our next post, we’ll explore:

You'll learn how to:

• Build these RPC types with real examples

• Implement them using Spring Boot

• Understand where and when to use each pattern

👉 Stay tuned for: Advanced gRPC in Spring Boot — Streaming and Beyond!

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