This document discusses GraphQL Federation as a way to combine multiple GraphQL APIs into a single federated graph. GraphQL Federation allows clients to interact with multiple microservices through a single GraphQL endpoint and query, retrieving necessary data in one request. It streamlines the request/response cycle while preserving client simplicity and performance. Individual teams can develop GraphQL APIs independently and contribute to the unified federated schema without needing to maintain separate API layers.

1. GraphQL Federation, the missing
piece of microservices
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2. 1
AlphaSense is a
AI-Powered Search
leading all-in-one market intelligence platform
headquarters in US
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as a top 50 AI company in
2023
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3. API Team
GraphQL Service Development &
Maintenance
GraphQL Federation Knowledge
Leaders & Educators
Exposing GraphQL APIs to
External Clients
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4. 4
Microservices are domain-based
monolith service services

5. 5
Monolith
async function runQuery() {
try {
const client = await
pool.connect();
const result: QueryResult =
await client.query('SELECT *
FROM your_table_name');
client.release();
} catch (error) {
console.error('Error
executing query:', error);
}
}
Presentation Layer Logic Layer Data Layer
Database

6. 6
Microservices
async function runQuery() {
try {
const client = await pool.connect();
const result: QueryResult = await
client.query('SELECT * FROM
your_table_name');
client.release();
} catch (error) {
console.error('Error executing query:',
error);
}
}
Database
APIs
User
async function runQuery() {
try {
const client = await pool.connect();
const result: QueryResult = await
client.query('SELECT * FROM
your_table_name');
client.release();
} catch (error) {
console.error('Error executing query:',
error);
}
}
Database
APIs
Search
async function runQuery() {
try {
const client = await pool.connect();
const result: QueryResult = await
client.query('SELECT * FROM
your_table_name');
client.release();
} catch (error) {
console.error('Error executing query:',
error);
}
}
Database
APIs
Watchlist
User team
Search team
Watchlist team

7. 7
Consider following example
Client wants to fetch user together with documents
and their watchlists
USER Service DOCUMENT Service WATCHLIST Service
GET /user/123
GET /documents?user_id=123
GET /watchlists?user_id=123
with RESTful API

8. 8
with GraphQL
USER Service
DOCUMENT Service
WATCHLIST Service
GraphQL Server
GraphQL Gateway
GraphQL Gateway
GraphQL Server
GraphQL simplifies data retrieval by allowing clients to fetch
information from multiple services using a single query.
With GraphQL, you can create a unified data responsecombining data from different
sources, making it much easier for clients to consume.

9. 10
REST APIs typically have multiple endpoints for retrieving data from the server, while
GraphQLhas a multiple single endpointto which queries are sent.
Benefits
GraphQLhelps avoidthe issues of 'over-fetching' (retrieving too much data) and 'under-
fetching' (retrieving too little data) that often occur in REST APIs."

10. 12
What is
GraphQL Federation?

11. 13
Normal GraphQL Server?
USER Service
DOCUMENT Service
WATCHLIST Service
GraphQL Server
All the graphql
will be defined
in here

12. 14
What is GraphQL Federation?
USER Service
DOCUMENT Service
WATCHLIST Service
GraphQL Gateway
Combine multipleGraphQL SubGraphs into
a single, federatedSuperGraph
This federated graphenables clients to interact
with multiple APIs through a single
request.

13. 15
Unified GraphQL API
It allows the combination of multiple GraphQL APIs into a single, federated graph. This means clients can interact with multiple APIs through just
one request, streamlining the request and response cycle
Other benefits
Preserving Client Simplicity and Performance
It eliminates the need for multiple requests to different non-federated GraphQL APIs, offering the advantage of fetching all necessary data in a single request, which is
particularly beneficial in scenarios where multiple teams develop APIs independently
Simplified Schema Design at Scale
Unlike other approaches that may complicate the federated schema, GraphQL Federation allows clients to interact with the federated schema as if it were a single,
monolithic structure. This simplifies both frontend and backend interactions
Single API Maintenance
Each team contributes to the federated GraphQL schema, working independently without the need to maintain multiple API layers. This approach centralizes quality
control and updates to a single platform team

14. 16
How to develop with GraphQL Federation?
GraphQL Gateway
USER Service
WATCHLIST Service
DOCUMENT Service
Git repositories CI/CD Pipeline
SuperGraph
Builder

15. 17
SuperGraph builder

16. 18
GraphQL Cosmo

17. Thanks!
Luc <dt@luc.vc>