For the team that has to run it.
.NET, PostgreSQL, Redis, Marten for documents and events, Wolverine for messaging and handlers, .NET Aspire for the local stack, a React interface.
PostgreSQL today. SQL Server is a supported path in the same library family, not yet proven by us. We say so plainly when asked.
Three services as containers: gateway, API and worker, built from one Dockerfile, plus a one-shot migrations job that runs before each release starts. The interface is a static bundle served by the edge proxy. The local developer stack is the same shape as production.
No managed service is required. Runs on any Kubernetes or on a pair of virtual machines. A bank that keeps its data on its own floor can.
The engine's lineage ran a 6,700-account structured book for twenty-five years and a 100,000-account consumer book in New Zealand. The architecture serves both shapes: a small complex book and a large retail operation. A measured figure for LedgerTM itself is published when we have one.
Day-end per tenant with a full run log; structured logging and health checks through .NET Aspire; one database to back up and restore.