Booking engine for UK businesses that sell 1-to-1 appointments: API, embeddable widget, owner dashboard and worker. Correct across UK clock changes.

• No double-bookings, enforced by the database. A PostgreSQL exclusion constraint: 100 parallel bookings for one slot → exactly 1 succeeds, 99 get 409.
• No lost emails. The booking and an outbox row commit in one transaction; a worker relays them with deterministic job ids and a send log.

✅ 183 tests · NestJS Next.js PostgreSQL Prisma BullMQ Redis

Live demo

Self-hosted job search workspace with an AI agent that runs as seven typed, schema-checked steps. It only prepares applications, never sends anything, and treats job page text as untrusted data to resist prompt injection.

• SSRF-safe job fetching. Every DNS answer is checked against private and cloud-metadata ranges, then the connection is pinned to the checked IP, so DNS rebinding can't swap it.
• Fixed a production memory incident. Streamed the 143k-row register in batches with one fixed INSERT … unnest instead of createMany, and capped the heap: worker memory 1 GB → ~250 MB.

✅ 92 tests · NestJS Next.js PostgreSQL Prisma BullMQ Zod

Live demo

Property and tenancy management for small landlords and letting agents, with a tenant portal and a contractor job page.

• Append-only rent ledger in integer pence. Mistakes are reversed, never edited, so the history always adds up.
• Idempotent daily rent job. A unique key on (tenancy, period start) means running it twice never charges twice, including due days on the 29th–31st.

✅ 115 tests · NestJS Next.js PostgreSQL Prisma BullMQ Redis

Live demo

Client document portal for firms that chase clients for paperwork: one secure link, upload from a phone, review and download.

• Per-file encryption. Each file has its own AES-256-GCM key, wrapped by a master key from the environment or AWS KMS.
• Scan before access. Uploads are virus-scanned on a BullMQ queue before staff can open them; client links are stored only as SHA-256 hashes.

✅ 79 tests · NestJS Next.js PostgreSQL Prisma BullMQ ClamAV

Live demo

Receptionist chat for small business websites. It answers only from the business's own knowledge and hands over to a person when unsure. Bring your own key.

• No cross-tenant retrieval. Vector search (pgvector) is filtered by workspace, so one business can never retrieve another's data.
• Real-time. Replies stream over WebSockets, and staff can take over a live conversation.

✅ 156 tests · NestJS Next.js PostgreSQL pgvector Socket.IO Redis

Live demo

Command-line tool for job seekers to search the UK Home Office register of licensed visa sponsors by name, city, route and industry.

• Streams, never loads. The full GOV.UK register is downloaded and parsed as a stream, and the new index is swapped in only after it passes checks.
• Fails clearly when the source changes. Every load checks the CSV columns and names any that GOV.UK renamed or removed.

✅ 137 tests, on Linux, macOS and Windows · TypeScript Node.js Commander Vitest

Read more