Systems that actually run

Hosts the company's own client websites on a single server and switches each one on or off from a checkbox in the panel, with recurring billing. Switching a site off takes effect in about eight seconds.

• Per-client master switch at the edge proxy (ForwardAuth): a checkbox in the panel became the on/off switch for the hosted sites, without touching a single container.
• Fail-open at the gate and fail-closed on the platform own site, as a documented decision: a database hiccup must never take down third-party sites hosted there.
• Middleware order chosen by measurement, the rate limiter deliberately sits before the gate, so a flood against one site never becomes a flood against the whole platform. The thresholds were calibrated against a real load test of 654 requests per second.
• Recurring billing with an idempotency key on checkout and customer reuse at the gateway, plus a manual override that exists only in code and wins over subscription status, the client cannot unlock themselves from the panel.
• Headless CMS serving content across domains: the client registers an entry in the panel and another client site reflects it with no redeploy; if the fetch fails, the section simply does not render.

You send a link or a photo over WhatsApp and get the finished post back for feed, story, carousel or reel, with the copy adjusted in conversation and an approval queue before publishing.

• The only interface is a WhatsApp conversation: not commands, but natural language rewriting the copy field by field (kicker, headline, highlight, subhead, call to action, caption and hashtags).
• HTML is the single authoring language: the same piece becomes a PNG through a headless render or an MP4 through a deterministic timeline, no step ever passes through a graphics editor.
• Real computer vision in the framing: offline face detection in roughly 100 ms with a 230 KB model, angle measured from the eye line and the bust crop computed geometrically rather than guessed by a language model. The background is then removed and the person composited between backdrop and frame.
• Publishing through the official Meta API, with the explicit decision not to use browser automation so the client account reach is never put at risk.
• A daily scheduler that sweeps news across the covered towns and offers the five hottest as posts, with a state queue (draft, generating, rendered, approved, published) and an approval dashboard.

The order leaves the table tablet or the waiter's phone and reaches the kitchen in real time over the local network, with no internet needed and each item going to the right printer.

• Runs with the internet down: local database in WAL mode and real-time updates over Socket.IO inside the venue. The cloud is never in the order path.
• Three operating modes (tablet at the table, order pad on the waiter phone, QR code for the customer) with per-device override, the choice is made per device, not by a global switch that changes the whole system.
• Over-the-air updates through a purpose-built C# launcher: it compares the remote version, downloads the package and replaces itself, with path-traversal protection on extraction and processes killed before any file is copied.
• Session secret generated on first boot on the customer machine (64 bytes, restricted permissions), the JWT secret is never baked into the distributed binary.
• Thermal printing routed by zone and product category: each item prints at the right station (kitchen, sushi bar, till) with nobody shouting the order across the room.

Every part's price comes from an in-house pricing engine, checked to the cent, with a catalogue, a discount calculator and pricing parameters editable in a table.

• Sessions in an HMAC-SHA256 signed cookie compared in constant time, httpOnly and scoped to the site. The signing secret is mandatory in production: without it the application refuses to start rather than falling back to a development value.
• The token carries a fingerprint of the credential: changing the admin password or a customer access code instantly invalidates every old session on every device, with no session table in the database.
• Access control in three layers, a middleware guard, per-request revalidation of the user in the layout (deleted, blocked or credential-changed drops straight to logout) and a check inside every server action. Each customer carries a role, a block flag, a confirmation flag and a separate permission for the pricing screen.
• Login and password recovery are rate-limited per email and per IP, with a single generic error that never reveals whether an address exists, and a single-use reset link that expires in 30 minutes because it embeds a fingerprint of the current password.
• Auditing and a small attack surface: every sign-in records date, user and device; uploads are admin-only with a MIME allowlist, a size cap and a randomised filename; the billing webhook is signature-verified and re-checked at source; transactional email leaves from a dedicated container on an internal network with no port exposed on the host.

Clocking-in, deliveries with photo and location, stock transfers and cash control on every employee's phone. It works offline and syncs on its own once the signal comes back.

• Offline sync resolves per field, not per record: two employees editing the same delivery from different places never overwrite each other, and every resolved conflict is written to an audit table.
• Mutation queue in IndexedDB that flushes on reconnect, on window focus and every 15 seconds, the driver records the drop-off in a signal blackspot and the data arrives intact.
• Three live integrations at once: tax ERP over OAuth, finance system with one credential pair per store entity, and a queue-orchestrated Playwright robot for the legacy portal that has no API.
• National ID numbers encrypted at rest, plus a data-protection endpoint that hands each employee their own record as JSON.
• Per-user theme is computed, not picked: the chosen colour generates the whole HSL palette and text contrast is decided by luminance (WCAG AA), injected server-side so nothing flashes on load.

Selling over the counter, on WhatsApp and online from one system: stock by colour, a store-credit ledger with partial payments and pricing for handmade pieces.

• Channel isolation on every order (counter, WhatsApp, online): the new shop never contaminates the till or the credit ledger, and the upgrade shipped with zero regression in what was already selling daily.
• Price and shipping are recalculated on the server, the value coming from the browser is never trusted. That fixed a genuine security flaw in the previous model.
• Stock is only decremented for good once payment is approved, with an idempotent webhook and oversell detection inside the SQL function itself, which evolved across three migrations.
• Self-service credential vault: the owner pastes her own payment and shipping keys into the admin, they sit in a table with row-level access policies, and the panel only reads a masked view returning "configured" plus the last four digits.
• Five Deno serverless functions for shipping quotes, checkout, payment webhook, label purchase and integration storage, no secret ever reaches the browser.