Subscriptions

The information on a page can change while someone is still reading it. A bookstore page, for example, might display whether a book is available to order. A query gives the page the current value, but that value can become stale. Repeated polling can refresh it, yet most requests may return unchanged data.

A subscription lets the client receive results as relevant events occur.

This chapter explains how GraphQL turns an event stream into selected results, how those results travel to clients, and which delivery and lifecycle decisions the application must make.