workers-best-practices

What the source does

• FilesystemNone observedNo reads or writes in the source
• NetworkNone observedNo outbound calls in the source
• ShellNone observedNo commands run in the source
• DependenciesPinnedNothing floats
• SecretsNone foundNo keys in source

Five audit layers

Gates applied: no behavioural pass.

Audit 0.4.1 · source sha b5f2fbcde9d0 · 29 Oct 2026Report an issue or request a re-scan

• Publishercloudflare GitHub organizationOwner of the repository this skill is read from
• Source foldercloudflare/skills/skills/workers-best-practicesThe exact folder we audited
• LicenceApache-2.0As the repository states it
• Commit pinned for this verdictb5f2fbcde9d0A new audit runs when the source changes
• Repository statusNot archivedPushed today
• Sandboxed runNot runSkills are read, not executed; layer L4 is skipped

Its description: Cloudflare Workers best practices for production applications. Use when writing, reviewing, or configuring Workers.

---
name: workers-best-practices
description: Cloudflare Workers best practices for production applications. Use when writing, reviewing, or configuring Workers.
---

Your knowledge of Cloudflare Workers APIs, types, and configuration may be outdated. **Prefer retrieval over pre-training** when writing or reviewing Workers code.

Use the project's installed versions, generated types, and Wrangler compatibility settings as the baseline for existing code. Retrieve relevant Cloudflare documentation to verify API, configuration, runtime behavior, and limit claims.

## References

Read the sections relevant to the task:

| Reference | When to use it |
|-----------|----------------|
| [Configuration and observability](references/configuration.md) | Compatibility dates, bindings, generated types, secrets, logs, and traces |
| [Runtime patterns](references/runtime-patterns.md) | Streaming, promise lifetime, request state, service calls, security, and runtime tests |
| [Platform API checks](references/platform-apis.md) | Handler signatures, platform classes, binding access, and serialization |

For missing evidence, consult [Workers best practices](https://developers.cloudflare.com/workers/best-practices/workers-best-practices/index.md) or find the affected product in the [Cloudflare docs directory](https://developers.cloudflare.com/directory/index.md). Use the installed Wrangler schema for config fields. A newer type package does not supersede the project's configured target.

## Keep Compatibility Dates Current

Use today's date for new Workers. Encourage periodic updates for existing Workers, reviewing compatibility changes and running relevant tests. Assess existing behavior against its configured date and flags; see [compatibility guidance](references/configuration.md#keep-compatibility_date-current).

## Enable Observability

Enable [Workers Logs](https://developers.cloudflare.com/workers/observability/logs/workers-logs/index.md) and [Traces](https://developers.cloudflare.com/workers/observability/traces/index.md) when creating or preparing a Worker for production. Set `observability.enabled` and `observability.traces.enabled` to `true`; the top-level setting alone does not enable traces. Use structured JSON logging and configure sampling for the workload. During reviews, flag missing logs or traces. See the [configuration example](references/configuration.md#enable-workers-logs-and-traces).

## Place Compute Near Regional Databases

For Workers that make multiple sequential queries to one regional database, configure explicit placement matching the database's provider and region before deployment. Ask for missing location information, preserve existing placement choices, and verify handler eligibility and deployed request duration. See [database placement](references/configuration.md#place-compute-near-regional-databases).

## Anti-Patterns to Flag

| Anti-pattern | Consequence and preferred pattern |
|-------------|-----------------------------------|
| `await response.text()` or similar buffering on unbounded data | Can exhaust Worker memory; [stream large or unbounded bodies](references/runtime-patterns.md#stream-request-and-response-bodies). |
| Hardcoded secrets in source or config | Leaks credentials through version control; use Wrangler secrets. |
| `Math.random()` for security-sensitive tokens or IDs | Predictable values; use `crypto.randomUUID()` or `crypto.getRandomValues()`. |
| Async work started without awaiting, returning, or attaching it to `ctx.waitUntil()` | Work can be dropped and errors missed; tie it to the request or background-work lifetime. |
| Module-level mutable request state | Leaks data across requests and can cause I/O ownership errors; pass request state explicitly. |
| Cloudflare REST API calls for operations available through Worker bindings | Adds network and authentication overhead; use the available binding. |
| `ctx.passThroughOnException()` used as general error handling | Can conceal Worker failures by forwarding to the origin; use explicit error handling and structured error responses. |
| Hand-written `Env` that duplicates Wrangler bindings | Can drift from configuration; generate binding types with `wrangler types`. |
| Direct string comparison of secret values | Can expose timing differences; use the [Web Crypto comparison pattern](references/runtime-patterns.md#use-web-crypto-for-secure-token-generation). |
| Destructuring `ctx` methods, such as `const { waitUntil } = ctx` | Loses the receiver; call `ctx.waitUntil(...)`. |
| `any` on `Env` or handler parameters | Hides binding and handler contract errors; use the project's generated and platform types. |
| `as unknown as T` to force a platform type match | Hides incompatibilities; fix the underlying contract. |
| `implements` used in place of extending a platform base class | Does not inherit runtime behavior, `this.ctx`, or `this.env`; use the appropriate base class. |
| Unbound `env.X` in a platform class method | Bindings are available through `this.env.X`; see [binding access patterns](references/platform-apis.md#binding-access--the-most-common-error). |
| Applying one serialization rule across Queues, Workflow steps, storage, and WebSockets | Can reject valid payloads or accept unsupported ones; check the [specific API and encoding](references/platform-apis.md#serialization-boundaries). |

## Validation

Use the project's existing checks for affected Workers behavior: type-check binding or handler contract changes, and run relevant runtime tests for behavior changes. Preserve required repository checks; a narrow edit does not require a full Workers audit.

## Scope

This skill covers Workers-specific best practices and code review. For related topics:

- **Durable Objects**: load the `durable-objects` skill
- **Workflows**: see [Rules of Workflows](https://developers.cloudflare.com/workflows/build/rules-of-workflows/index.md)
- **CLI commands**: load the `cf-cli` skill, or the `wrangler` skil

Excerpt, first 6,000 characters of SKILL.md, verbatim from the audited commit. It is text from someone else’s repository, quoted so you can judge it before your agent reads it.

git clone https://github.com/cloudflare/skills
git -C skills checkout b5f2fbcde9d0

Works in

1. 2026-10-29
   ✓SAFE B 89 / 100

   first audit · source b5f2fbcde9d0

Questions about workers-best-practices

• github.com/cloudflare/skills/tree/main/skills/workers-best-pract — the audited source at commit b5f2fbcde9d0 and every finding aboveObserved · 29 Oct 2026

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