The Wire Fence

The bus has no broker. There is no EchoMQ process sitting between a client and the data, no bespoke wire format to serialize, no SDK to port to a new language. The protocol is Valkey commands and inline Lua, declared behind one version fence — echomq:3.0.0 — and that is the whole interface. A peer conforms to the fence, not to a client library, because there is no client library to conform to: there is the database's own wire, and a version number stamped on it.

That single fact is what makes the bus polyglot, and polyglot is not an aspiration here — it is a tested property. Because every runtime already ships a Valkey client, every runtime is a first-class peer the moment it issues the same commands against the same keys. A Go worker and a BEAM node are not bridged; they are equals on one group. The conformance suite makes the equality concrete: it stands a non-BEAM reader in the same consumer group as the BEAM consumers and drains the same pending-entries list — the seam demonstrated on the wire, not asserted in a doc.

The version on the fence is not decoration; it is a contract about change. Adding a command — a new verb inside one of the twelve families — is additive: old peers never issued it, so they keep working untouched. That is a protocol minor, and minors are cheap. Changing what an existing byte on the wire means — a key's shape, a field's order, a lease's encoding — is a major, because a peer built against the old meaning now reads the new bytes wrong. The fence makes the two kinds of change impossible to confuse: a peer checks the version and knows exactly which contract it is holding.

This is why a rung that re-drives a shipped script freezes the script's bytes to the last shipped version and proves it — a re-use rung is not allowed to quietly turn a minor into a major. The wire is hard-pinned because it broke once, and the lesson was not merely to fix that break; it was to make silent breaks structurally impossible. The polyglot promise depends on it: a Go peer trusts echomq:3.0.0 to mean today what it meant yesterday, and the fence is the mechanism that keeps that trust honest across every runtime on the group.

The wire rule — the protocol is the database's own wire, so any runtime that speaks it is a peer. No broker to port, no library to bless: a peer conforms to the version fence, not an SDK. Additive change is a minor and old peers keep working; changing what a byte means is a major and the fence is what makes the difference impossible to miss.