Subscription lifecycle in GraphQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a subscription in GraphQL?

A subscription in GraphQL is a way to get real-time updates from the server. It keeps a connection open and sends data to the client whenever an event happens.

beginner

What happens when a client starts a subscription?

When a client starts a subscription, it opens a persistent connection to the server, usually over WebSocket, to listen for specific events or data changes.

intermediate

How does the server send data during a subscription?

The server sends data to the client whenever the subscribed event occurs. This data is sent as a stream of messages over the open connection.

intermediate

What is the role of WebSocket in GraphQL subscriptions?

WebSocket provides a full-duplex communication channel that stays open, allowing the server to push updates to the client instantly during a subscription.

beginner

How does a client stop a subscription?

A client stops a subscription by closing the connection or sending an unsubscribe message, which tells the server to stop sending updates.

What does a GraphQL subscription do?

A Provides real-time updates from the server

B Fetches data once like a query

C Deletes data on the server

D Updates data on the client only

Subscriptions keep a connection open to receive real-time data updates from the server.

Which protocol is commonly used to keep a subscription connection open?

A SMTP

B FTP

C HTTP GET

D WebSocket

WebSocket allows full-duplex communication needed for real-time subscriptions.

When does the server send data in a subscription?

A Whenever the subscribed event happens

B Only when the client requests it

C At fixed time intervals

D Only once at the start

The server pushes data to the client whenever the event the client subscribed to occurs.

How does a client end a subscription?

A By sending a query

B By refreshing the page

C By closing the connection or unsubscribing

D By sending a mutation

Closing the connection or sending an unsubscribe message stops the subscription.

What is the main benefit of using subscriptions?

A Faster database writes

B Real-time data updates without polling

C Simpler queries

D Better security

Subscriptions provide real-time updates without the need for repeated polling.

Explain the lifecycle of a GraphQL subscription from start to finish.

Think about how the connection starts, how data flows, and how it ends.

Describe why WebSocket is important for GraphQL subscriptions.

Consider how data moves between client and server continuously.