---
title: Best practices
description: Best practices for using Flagship in applications, including evaluation paths, rollout workflows, and safe flag cleanup.
image: https://developers.cloudflare.com/dev-products-preview.png
---

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# Best practices

Use these patterns to keep Flagship evaluations predictable, fast, and easy to maintain.

## Choose the right evaluation path

Use the [Workers binding](https://developers.cloudflare.com/flagship/binding/) inside Cloudflare Workers. The binding handles authentication automatically and avoids application-managed API tokens.

Use the [OpenFeature SDK](https://developers.cloudflare.com/flagship/sdk/) when you run outside Workers or need a vendor-neutral OpenFeature interface. In Workers, you can still pass the binding to the OpenFeature server provider to keep binding performance while using OpenFeature APIs.

## Evaluate once per request

Avoid evaluating the same flag repeatedly in a loop. Evaluate the flag once, store the result in a local variable, and reuse it for the rest of the request.

TypeScript

```
const enabled = await env.FLAGS.getBooleanValue("show-related-items", false, {  userId,});
for (const item of items) {  if (enabled) {    item.related = await loadRelatedItems(item.id);  }}
```

## Pass context consistently

Targeting and percentage rollouts depend on the evaluation context you pass from your application. Use stable identifiers and the same attribute names everywhere.

TypeScript

```
const context = {  userId: session.user.id,  plan: session.user.plan,  country: request.cf?.country ?? "unknown",};
const enabled = await env.FLAGS.getBooleanValue("new-checkout", false, context);
```

For OpenFeature SDKs, use `targetingKey` as the stable identifier. For the Workers binding, use the attribute configured for your rollout, such as `userId`.

## Choose safe defaults

Every evaluation method requires a default value. Choose a default that keeps your application safe if the flag does not exist, cannot be evaluated, or has a type mismatch.

For release flags, this is usually the existing experience. For configuration flags, choose conservative limits or behavior that your application can handle without extra dependencies.

## Use details for debugging and observability

Use `*Details` methods when you need to understand why a value was returned. Details include the resolved value, variant, reason, and error metadata.

TypeScript

```
const details = await env.FLAGS.getBooleanDetails("new-checkout", false, {  userId: "user-42",});
console.log(details.value);console.log(details.variant);console.log(details.reason);console.log(details.errorCode);
```

## Roll out progressively

Start with a small percentage rollout, monitor application metrics, then increase the percentage over time.

1. Create the flag with a small rollout, such as 5%.
2. Monitor errors, latency, business metrics, and user feedback.
3. Increase to 25%, then 50%, then 100% as confidence grows.
4. After the rollout reaches 100%, make the winning variant the default and remove temporary targeting rules.
5. After the feature is fully shipped, remove the old code path and delete the flag.

## Clean up stale flags

Flags that are disabled or fully rolled out still add maintenance cost. Before deleting a flag, disable it first, monitor for unexpected behavior, remove the evaluation code, deploy the code change, then delete the flag from Flagship.

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