gRPC is a high-performance, open-source communication framework designed by Google for efficient communication between distributed systems. It is especially popular in microservices, cloud-native architectures, IoT, and low-latency systems.

1. What is gRPC?

gRPC stands for Google Remote Procedure Call. It allows a service running on one machine to directly invoke a method on another machine as if it were a normal local function call. The network layer complexities are abstracted away.

Important characteristics

• RPC-based communication
  • Instead of “resources” (REST), gRPC uses “remote procedures”.
  • You define functions such as CreateUser, GetOrder, ProcessPayment, etc.
  • Clients call these functions directly, and gRPC handles the networking.
• Strongly-typed contract-first design
  • gRPC uses Protocol Buffers (Protobuf) to define message structures and services.
  • This ensures consistency across teams and languages.
• Language Neutrality
  • The same .proto file can generate client/server code in multiple languages—Java, Python, Go, C#, C++, Node.js, PHP, Ruby, Kotlin, Swift, even Rust.
• Used over HTTP/2
  • HTTP/2 enables multiplexing, header compression, bidirectional streaming, and reduced latency.

2. Why gRPC is Faster than REST

Below are the technical reasons behind gRPC’s speed:

2.1 Binary Protocol Instead of Text

REST uses JSON:

{
  "name": "Samir",
  "age": 63
}

JSON is:

• Verbose
• Text-based
• Slower to parse
• Larger in size

gRPC uses binary Protobuf, which looks like this internally:

[field_number][wire_type][encoded_value]

This is extremely compact and efficient for serialization/deserialization.

2.2 HTTP/2 Multiplexing

A text diagram of how HTTP/1.1 vs HTTP/2 works:

HTTP/1.1
========
Connection 1: Request A → Response A  
Connection 2: Request B → Response B  
Connection 3: Request C → Response C  

HTTP/2
======
Single Connection:
  |-- Stream A: Request A → Response A
  |-- Stream B: Request B → Response B
  |-- Stream C: Request C → Response C

Benefits:

• Multiple parallel requests over one connection
• No “head-of-line” blocking
• Lower latency
• Fewer system resources needed (CPU, sockets)

2.3 Header Compression

HTTP/2 compresses headers, allowing smaller request/response sizes.
REST APIs often send repeated long headers; gRPC avoids that overhead.

2.4 Built-in Streaming

REST is limited to a single request/response cycle.
gRPC supports four communication types (explained later), enabling more efficient real-time applications.

3. gRPC Architecture

Below is a conceptual architecture diagram in text form:

     ┌──────────────────────────────┐
     │         Client App           │
     └─────────────┬────────────────┘
                   │
           (Generated Client Stub)
                   │
            ┌──────▼───────┐
            │   gRPC API    │
            └──────┬───────┘
             HTTP/2 │ Protobuf
                   │
            ┌──────▼───────┐
            │   Network     │
            └──────┬───────┘
             HTTP/2 │ Protobuf
                   │
            ┌──────▼────────┐
            │    gRPC API    │
            └──────┬────────┘
           (Generated Server Stub)
                   │
     ┌─────────────▼────────────────┐
     │          Server App           │
     └───────────────────────────────┘

Explanation of each layer

1. Client Stub
   Automatically generated glue code that exposes remote methods as local methods.
2. gRPC Runtime
   Handles:
   • Serialization
   • Deserialization
   • Connection pooling
   • Stream handling
   • Retries and deadlines
3. HTTP/2 Transport Layer
   Sends binary frames over the network.
4. Server Stub
   Converts incoming binary data into structured method calls.

4. Protocol Buffers (Protobuf) in Detail

Protobuf is the heart of gRPC. Key characteristics:

Compact Binary Serialization

Fields are stored as tag-value pairs, making them extremely small compared to JSON or XML.

Strongly Typed

You define message fields with fixed data types:

• integers
• floats
• strings
• booleans
• nested messages
• enumerations

This eliminates ambiguity.

Backward and Forward Compatibility

A critically important feature.

Example diagram explaining compatibility:

Version 1:             Version 2:
----------             -----------

message Person {       message Person {
  string name = 1;     string name = 1;
  int32 age = 2;       int32 age = 2;
}                      string email = 3;  <-- Added new field
                       int32 height = 4;  <-- Added new field
}

Older clients simply ignore fields they don’t understand.
Newer clients accept older messages because missing fields are given defaults.

5. Types of gRPC Communication

gRPC supports 4 types of messaging patterns, each designed for specific scenarios.

5.1 Unary RPC

Client → (single request) → Server
Server → (single response) → Client

Use cases:

• Fetching a single user
• Submitting a form
• Simple CRUD operations

This is the most REST-like pattern.

5.2 Server Streaming RPC

Client → one request → Server
Server → continuous stream of responses → Client

Text diagram:

Client -----------------> Server
         Request

Client <------ Response 1
Client <------ Response 2
Client <------ Response 3
        (and so on...)

Use cases:

• Stock market ticker
• Order updates
• Live logs streaming
• Sending a large dataset in chunks

5.3 Client Streaming RPC

Client → continuous stream of requests → Server
Server → one final response → Client

Diagram:

Client ---- Req1 ------>
Client ---- Req2 ------>
Client ---- Req3 ------>
               Server
Client <---- Final Response

Use cases:

• Uploading large files in chunks
• IoT devices sending telemetry data
• Batch processing of events

5.4 Bidirectional Streaming RPC

This is the most powerful mode.

Client ↔ continuous stream ↔ Server

Diagram:

Client -----> Req1 ------------------>
       <----- Resp1 <---------------- Server
Client -----> Req2 ------------------>
       <----- Resp2 <---------------- Server

Both ends communicate independently and simultaneously.

Use cases:

• Real-time chat systems
• Video/audio conferencing
• Multiplayer gaming events
• Collaborative editing (Google Docs-like)
• Trading applications with live bid/ask updates

6. Backward Compatibility Rules (Important for APIs)

Protobuf allows APIs to evolve without breaking existing users.

Safe operations (allowed)

• Adding new fields
• Marking fields as optional
• Deprecating fields using reserved
• Changing default values

Unsafe operations (not allowed)

• Changing existing field numbers
• Changing field types inconsistently
• Reusing removed field numbers for new fields

This makes gRPC highly suitable for large-scale APIs with many versions.

7. gRPC vs REST

Category	REST	gRPC
Underlying Protocol	HTTP/1.1	HTTP/2
Message Format	JSON (text-based)	Protobuf (binary)
Speed	Slower	Very fast
Streaming	Limited	Fully supported
API Definition	Often unstructured	Strong contract via .proto
Browser Support	Excellent	Requires gRPC-Web
Payload Size	Larger	Much smaller
Error Model	Loose, inconsistent	Standard, structured
Tooling	Postman, Swagger	Reflection, health checks, interceptors

When gRPC is ideal:

• Microservices talking to each other
• High-performance backend systems
• Low-latency streaming
• Multi-language environments
• Real-time systems

When REST is better:

• Public APIs
• Browser-based consumers
• Simple CRUD applications

8. Real-World Use Cases of gRPC

Cloud-native architectures

Most cloud platforms like Google Cloud, Kubernetes, and Envoy use gRPC internally.

Microservices at large companies

Netflix, Dropbox, Square, Cisco, and Spotify use gRPC heavily for internal communication.

Complex distributed systems

gRPC’s low latency and structured communication is ideal for:

• Payment gateways
• Fraud detection systems
• Driver-location updates (ride-sharing apps)
• Order-book updates in trading systems

IoT

Devices send data frequently but require small message size → perfect match for Protobuf.