Concepts

Term	Meaning
Organization	The billing entity. Owns a plan, members, API keys, the audit log and (optionally) a signed BAA. Every API path is scoped to an org.
Project	A folder of instances inside an org. Projects belong to a team on Team and Enterprise.
Instance	One database server: an engine, a version, a size, a region and a placement. It has its own hostname, credentials, allow-list, backups and metering.
Engine	One of the 18 database engines in the catalogue. Five are available today; the rest are on the roadmap.
Size	A CPU and memory shape from f0 to xl32, with its own hourly price (size catalogue).
Cell	A Kubernetes cluster that runs instances of exactly one tier: free, standard or hipaa. Tiers never share a cluster, bucket, key or gateway fleet.
Placement	Where an instance runs: shared (a shared node pool), dedicated-node (a node pool for your org, Team and Enterprise) or secure (a HIPAA cell on your own node pool, Team and Enterprise with a signed BAA).
Secure hosting	The secure placement: dedicated nodes, per-org customer-managed keys, immutable backups, audit export and a Business Associate Agreement. It is per instance, not per account.
Gateway	The TLS-terminating proxy in front of every cell. It routes by SNI, enforces allow-lists and connection limits, meters egress and re-encrypts to the pod.
Pause	Scale to zero while keeping storage; wake on demand. Free instances pause automatically after 15 idle minutes.
Plan	Free, Solo, Team or Enterprise. Sets the monthly fee, quotas, included usage and features; Solo and Team include one instance and bill each extra running instance per hour at its size price (usage and billing).
Compute unit (CU)	One vCPU with 4 GiB. A capacity measure shown in usage charts; it does not set the price.

How a request flows

your app ──TLS──► gateway (allow-list, SNI route, meter) ──mTLS──► engine pod in its own namespace
                    │
                    └── control plane (api, provisioner, operator) never touches the data path

The control plane creates and reconciles instances; it never proxies queries and never stores instance credentials, only references to secrets that live inside the cell. See Data confidentiality.