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Precomputed Assignments

Overview​

Precomputed assignments is an execution mode that allows you to receive assignments for all flags for a given user.

The computation happens with a remote call to an Eppo Edge Function which is globally distributed to be as close to the user as possible. Availability is backed by Eppo's CDN.

This mode is best suited for applications that require a smaller response payload, more predictable latency, and removal of private targeting rules over the public internet.

The new SDK methods are available in Eppo's Javascript SDK version 3.8.2 and above.

Advantages​

  • Private and secure handling of targeting rules.
  • High availability and low latency due to globally distribution with the CDN.

Prerequisites​

On client initialization, you must have the subject key and all subject attributes available.

Assignment logging​

Using the non-precomputed Eppo client, flag evaluation and assignments both occur together in the client.

When using the precomputed Eppo client, flag evaluation occurs up front during initialization and assignments occur afterwards.

In both case, assignment events are only logged by the provided logging callback when get*Assignment is invoked.

Initialize precomputed client​

import * as EppoSdk from "@eppo/js-client-sdk";

// Define logAssignment so that it logs events
const assignmentLogger: IAssignmentLogger = {
  logAssignment(assignment) {
	console.log(assignment);
  }
};

// Initialize the client
const client = await EppoSdk.precomputedInit({
    apiKey: 'YOUR_SDK_KEY',
    assignmentLogger: assignmentLogger,
    subjectKey: 'test-subject',
    subjectAttributes: { attr1: 'value1' },
});

Perform evaluation​

After the precomputed Eppo client is initialized, the client instance can be accessed anywhere in your application.

get*Assignment looks up the precomputed assignment and returns it immediately, or returns the default value if the precomputed assignment is missing.

const client = EppoSdk.getPrecomputedInstance();
const variant = client.getStringAssignment(flagKey, 'default-value');