Request Deduplication

When multiple components request the same resource at the same moment, WELD detects the duplicate and binds all callers to a single in-flight Promise instead of firing N requests to the server.

The problem it solves

Imagine a dashboard with 3 components that all need the current user’s data on mount:

// Component A
const user = await api.get('v1/me').promise

// Component B (mounts at the same time)
const user = await api.get('v1/me').promise

// Component C (mounts at the same time)
const user = await api.get('v1/me').promise

Without deduplication: 3 network requests hit your server simultaneously.
With WELD: 1 network request, all three components get the same result.

How it works

WELD generates a deterministic cache key from the request method, URL, query params, and body. If a request with that key is already in flight, the new caller gets the existing Promise back instead of starting a new one.

Request A → key: "GET::/v1/me::::" → no match → starts fetch, registers Promise
Request B → key: "GET::/v1/me::::" → match found → returns existing Promise
Request C → key: "GET::/v1/me::::" → match found → returns existing Promise

Server receives: 1 request
All 3 callers receive: same data

Once the Promise settles (success or error), it’s removed from the map automatically.

Deduplication is on by default

You don’t need to configure anything. It’s active for all GET requests automatically.

// These three calls — even from different components — share one request
api.get('v1/products', Schema)
api.get('v1/products', Schema)
api.get('v1/products', Schema)

Disabling it

const { promise } = api.get('v1/products', Schema, {
  deduplicate: false, // always fires a new request
})