gatecrashAn entire event from one Raspberry Pi

Ticket validation at every gate, the control-room dashboard, every attendee's wallet, and Bluetooth mesh chat between phones — with no internet at all.

Try it in one command

What it is

GitHub

Exactly once, and provable

Ten scanners hammering one QR is a single SQLite compare-and-set. That statement is the linearization point of the whole system, and every admission can be proved to somebody who does not trust the box with sixteen hashes.

How a scan is decided

Honest about CAP

When a gate cannot reach the box, something has to give. STRICT stops admitting; DEGRADED keeps the queue moving and detects every double use within seconds of the network healing. The choice is in the signed manifest, not a default somebody discovers at a door.

When the box is unreachable

Built for the power going out

The box is a Pi in a cupboard behind a bar. The simulator pulls its plug hundreds of times a run and asserts that no acknowledged scan is ever lost, that the control room is not signed out, and that occupancy comes back as the truth rather than zero.

Correctness

Readable across a queue

A guard at 22:00 is watching people, not a phone. A scan floods the screen with one colour and one glyph, plays a two-note rise or a low buzz, and vibrates in a pattern you can tell apart through a jacket. Text is the third channel.

At the gate

Chat with no signal

Twenty thousand phones in a field is a dead network. Backstage is a Bluetooth mesh with passphrase channels, X25519 direct messages, signed announcements and a friend finder — and the venue boxes bridge the islands over the LAN.

Mesh chat

A venue, not a door

Zones with prerequisites, per-tier door allowlists, seated sections laid out along a curve, and Dijkstra wayfinding with a step-free variant. A pit wristband scanned before the outer gate is refused with directions.

Zones, seats and doors

The numbers

Every one of these is produced by something in the repository, and the command that produces it is next to it in the README.


Box binary, `linux/arm64`	12.3 MB, statically linked
Scans per second, over HTTP	~2,300
Seeded event-days with zero invariant violations	240,000 scans, 472 power cuts, 5,000 double uses all detected
Mesh delivery, 5,000 phones	99.4%, p95 556ms
Offline filter, 50,000 tickets	175 KB, 49ns lookups
Attendee wallet, gzipped	77 KB of JavaScript

What it is not

No cloud during the event. No per-ticket fee. No account for an attendee, and no personal data on the box — it knows ticket ids and nothing else. No Docker, because the appeal is a machine with no runtime on it. No automatic updates, because a box that upgrades itself upgrades itself during a show.

It is also not a stadium product, and the capacity table says where it stops.