A screenshot tells you somebody can draw a form. It tells you nothing about whether the system behind it survives two people clicking at the same moment, or a government API timing out at the worst possible time.
So here are the diagrams instead. These are our own products, built and operated by us, which means we can describe how they work without asking a client for permission.
Sales, inventory, invoicing, payments and accounting are separate services. They deploy independently and talk over an event bus, so a failure in one does not stop a cashier taking money at the counter. Every request enters through a single gateway that resolves authentication, role permissions and which tenant the caller belongs to.
Roughly 428,000 hand-written lines. Multi-tenant, with 92 granular permissions, signed tokens verified again at every service, and a transactional outbox so an event is never lost between a database commit and the message bus.
Peru requires every invoice to be generated in a specified XML format, signed with the issuing company's own digital certificate, submitted to the revenue service, and reconciled against the response it returns. We built that whole path ourselves, with no third-party library.
This is the part that transfers. Swap the tax authority for a clearinghouse, a payments network or a health claims processor and the engineering is the same: a regulated counterparty, signed documents, per-tenant credentials, asynchronous acknowledgements and an audit trail that has to survive an inspection.
In our booking product, the rule that stops two appointments landing on the same resource at the same time does not live in application code. It lives in the database, as a constraint the engine cannot talk its way around. It holds whether the booking arrives from the public site, the business panel, our API or a widget embedded on someone else's page.
And it is proven rather than asserted: an automated test fires concurrent bookings from two real database connections on every deploy, and checks that exactly one wins.
Every store gets its own domain and its own branding, and the platform resolves which tenant to render from the incoming host header, rewriting internally so the visitor never sees a platform URL. Each tenant's data sits in a separate database project rather than a shared table with a tenant column, which is a stronger isolation guarantee than most platforms this size offer.
A tablet menu on the table and a keyboard-driven kitchen screen on the line, connected through a shared order schema. Tickets reopen automatically when a table orders more, enforced by a database trigger so the rule holds no matter which client inserted the item. Dispatching a ticket requires a deliberate confirmation, because a cook moving fast should not be able to clear a table by accident.
A small multi-tenant service that absorbs the fiddly parts of browser push: a signing key pair per project, a browser SDK that fetches the public key rather than hardcoding it, recovery when an existing subscription was made with a stale key, and automatic cleanup of dead endpoints.
Bring us the hard part. The first call is with an engineer, and you will get an opinion rather than a brochure.
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