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Core concepts

The mental model — the control plane as the span and your nodes as the piers, plus sizes, replicas, regions, and the datastore.

A handful of ideas explain almost everything about how Longbridge Control Plane works and what you pay for.

The span and the piers

Think of a bridge. The control plane is the span — the engineered part that has to stay up. Your nodes are the piers — they hold the real load, and they’re yours.

Longbridge runs the span: API server, scheduler, controller manager, the datastore, certificates, and version upgrades. You provide the piers: any machines you like, anywhere, joined over an outbound-only tunnel so they work behind NAT without a public IP.

Sizes

A control plane comes in sizes — small, medium, large — and each size is exactly double the one before it (control-plane CPU, memory, and datastore capacity). Pick a size the way you’d pick an instance type. If you outgrow one, move up; we prompt you before you hit a wall, never bill you by surprise.

Node count is guidance, not a hard cap. A small is comfortable for around five nodes; you’re free to run more, bounded by the control plane’s resources rather than a license check. See Sizes & pricing for the envelopes.

Replicas and redundancy

A cluster runs one control-plane replica by default. Add replicas — at the same per-replica price — and the control plane scales out and can shrug off a lost replica or a lost management node.

We call that control-plane redundancy. We deliberately don’t call it “high availability” until your datastore is redundant too; the same clusters graduate to HA later with no price change. We don’t use the word until it’s true. More in Scaling & redundancy.

Regions

Each control plane lives in a region (for example eu-hel, Helsinki). Your nodes can be anywhere — the region is where the managed control plane runs, not where your compute has to be. EU regions keep the control plane and its state in EU jurisdiction.

The datastore

Cluster state lives in a managed datastore that we run, back up, and (for the redundancy tier) replicate. You never operate etcd, take snapshots by hand, or get paged at 3 a.m. for a full disk — that’s the part we’re here to carry.

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