GraphQL and gRPC
Explore alternative API styles like GraphQL for flexible data fetching and gRPC for high-performance communication.
GraphQL and gRPC is a free System Design Basics for Backend Developers lesson on CoddyKit — lesson 2 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the System Design Basics for Backend Developers learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Beyond REST: GraphQL & gRPC
RESTful APIs are widely used, but they aren't always the perfect fit for every scenario.
Sometimes, you need more control over data fetching or require extremely high performance for inter-service communication.
This lesson explores two powerful alternatives: GraphQL and gRPC.
REST's Data Fetching Hurdles
Traditional REST APIs often lead to two common issues:
- Over-fetching: Receiving more data than needed in a single request, wasting bandwidth.
- Under-fetching: Needing to make multiple requests to different endpoints to gather all required data.
This can be inefficient, especially for mobile clients or complex UIs.
GraphQL: Query Exactly What You Need
GraphQL is a query language for your API, and a server-side runtime for executing those queries.
It empowers clients to request precisely the data they need, eliminating over-fetching and under-fetching.
Think of it as filling out a form for your data request, rather than accepting a pre-defined bundle.
Defining Data with GraphQL Schema
Every GraphQL API is built around a schema. This schema defines all the types of data and operations (queries, mutations) available.
It acts as a contract between the client and the server, ensuring clients know exactly what they can ask for.
Here's a simple example:
type User {
id: ID!
name: String!
email: String
posts: [Post]
}
type Post {
id: ID!
title: String!
content: String
author: User!
}Fetching Data with GraphQL Queries
Clients use GraphQL queries to fetch data. They specify the exact fields they want from the available types defined in the schema.
This means a single query can replace multiple REST requests.
See how we only ask for name, email, and post titles:
query GetUserAndPosts {
user(id: "123") {
name
email
posts {
title
}
}
}Changing Data with GraphQL Mutations
Just as queries fetch data, mutations are used to modify data on the server. This includes creating, updating, or deleting records.
Mutations also return data, often the newly created or updated object, confirming the change.
Here's an example to create a new post:
mutation CreatePost($title: String!, $authorId: ID!) {
createPost(title: $title, authorId: $authorId) {
id
title
}
}gRPC: High-Performance RPC
gRPC (Google Remote Procedure Call) is an open-source framework for high-performance communication between services.
Unlike GraphQL, gRPC is more commonly used for internal microservice communication where speed, efficiency, and strict contracts are paramount.
It's built on HTTP/2 for transport and Protocol Buffers for message serialization.
Protocol Buffers: gRPC's IDL
gRPC uses Protocol Buffers (Protobuf) as its Interface Definition Language (IDL) and its underlying message interchange format.
Protobuf defines the structure of your data and the service interfaces in a language-agnostic way.
This definition is then used to generate client and server code in various languages.
syntax = "proto3";
package greeter;
service Greeter {
rpc SayHello (HelloRequest) returns (HelloReply);
}
message HelloRequest {
string name = 1;
}
message HelloReply {
string message = 1;
}gRPC: Binary, HTTP/2, Streaming
Key features of gRPC for high performance:
- HTTP/2: Enables multiplexing (multiple requests over one connection) and bidirectional streaming.
- Binary Serialization: Protobuf serializes data into a compact binary format, which is faster and smaller than JSON.
- Code Generation: Automatically generates client and server stub code from
.protodefinitions, simplifying development.
Choosing Between GraphQL & gRPC
When to use which?
- GraphQL: Ideal for flexible, client-facing APIs where clients need to define their data requirements. Excellent for mobile apps and complex UIs.
- gRPC: Best for high-performance, low-latency inter-service communication (e.g., microservices), or when strict contracts and efficient data transfer are critical.
They solve different problems and can even be used together in a larger system!
Quick Check: API Styles
Consider a scenario where you are building a new mobile application with a complex UI that needs to fetch varied data from a backend with minimal network requests. Which API style would be most suitable for the client-server communication?
Recap: Flexible & Fast APIs
In this lesson, we explored two powerful API alternatives: GraphQL and gRPC.
- GraphQL provides a flexible query language, allowing clients to fetch precisely the data they need, tackling over- and under-fetching issues.
- gRPC offers a high-performance, binary communication framework, ideal for efficient inter-service communication using HTTP/2 and Protocol Buffers.
Understanding their strengths helps you choose the right tool for different system design challenges.
Frequently asked questions
Is the “GraphQL and gRPC” lesson free?
Yes — the full text of “GraphQL and gRPC” is free to read here on the web, and the System Design Basics for Backend Developers course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the System Design Basics for Backend Developers course, upgrade to CoddyKit PRO.
What will I learn in “GraphQL and gRPC”?
Explore alternative API styles like GraphQL for flexible data fetching and gRPC for high-performance communication. You practise System Design Basics for Backend Developers with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start System Design Basics for Backend Developers?
No prior experience is required. System Design Basics for Backend Developers on CoddyKit is structured for beginners through advanced learners; this is — lesson 2 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “GraphQL and gRPC” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this System Design Basics for Backend Developers lesson?
Yes. Every System Design Basics for Backend Developers lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.