Workers

works, rough edges

A worker runs your Worker script on workerd, the same runtime Cloudflare runs, driven through the Miniflare package. Cold start measured at p50 299ms, p95 321ms on an Apple M5 Pro, 2026-08-10.

Deploy

cd ./my-worker
hobby deploy

A wrangler.toml, wrangler.jsonc or wrangler.json in the directory is what makes it a worker rather than an app. Your existing wrangler manifest is read directly; there is no second config format to learn.

What is honoured, and what is ignored

Your manifest is for a platform with regions, tiers and a global network. This is one box. Rather than fail on the keys that cannot mean anything here, packages/worker/src/manifest.ts reads what it can and reports the rest as explicitly ignored, with the reason.

For example queues.consumers.max_concurrency is ignored and honoured as 1, because there is one box and one consumer container. A dead letter queue named by something other than a string queue name is ignored, and the consumer ends up with none.

Read the ignored list after your first deploy. A silently dropped setting is the failure mode this is designed to avoid.

Bindings

Binding	State
Durable Objects	Works, and alarms survive a sleep
KV, R2, D1, Cache	Work, persisted under the resource’s state directory
Queues, consuming	Works. A message wakes a sleeping consumer
Queues, producing	Broken on Linux. Why
Hyperdrive	Works, pointed at a Postgres resource in the same project

Where state lives

~/.hobby/projects/blog/api/
  bundle/    the built script and the manifest generated from your wrangler file
  state/     KV, R2, D1, cache
  do/        Durable Object sqlite, one directory per namespace

Each namespace directory also holds Miniflare’s own metadata.sqlite, which is not an object.

The runtime, honestly

Miniflare’s own documentation says it is a development tool. ADR 0011 runs it as a server anyway, records that this is what it is doing, and names the fallback: drop Miniflare from the runtime path and generate workerd capnp configuration directly, at the cost of the KV, R2 and D1 storage APIs.

It is pinned to 4.20260730.0, because npm’s latest is a 5.x alpha.

Two things learned by running it, worth knowing if you are debugging a build:

• Miniflare does not work under Bun. It asserts on a control pipe file descriptor that Bun’s child_process does not provide. The worker image is therefore two stages: Bun builds, Node runs.
• workerd ships no musl binary. On Alpine it fails with an ENOENT on the workerd binary, which reads like a missing file and is a missing platform.

Eject

hobby eject blog

You get the built bundle, the manifest, and the storage directories. A worker is not as portable as a Postgres data directory, because workerd is the thing running it, but nothing is held hostage.