Convert Web App to Multi-Tenant SaaS

JOB TYPE Fixed price, milestone-based, tied to written acceptance gates. Longer engagement for the right developer. DESCRIPTION We run a working practice-management web application, used daily by a UK accountancy firm. You will convert it into a multi-tenant SaaS we license to other UK firms - taking a working system and making it safely multi-firm, self-serve and billable, without breaking what already works. Current stack: Cloudflare Pages + Workers, data in Cloudflare KV (around 3,000 records plus documents), a large single-page front end. Existing integrations: Companies House, a screening API, Microsoft Graph email, a PDF/e-sign service. THE SCOPE YOU ARE PRICING 1. One central Postgres-class database (your choice of provider), one shared schema, row-level security enforced at the database, full tenants/users/roles structure, per-tenant branding. Automated cross-tenant isolation tests are an acceptance gate. 2. Migration of the existing firm in as the first tenant - count-verified, documents matched with an exceptions report, one supervised cutover, rollback retained. 3. Replace Cloudflare Access with a proper customer auth provider. 4. Tenant-isolated file storage, automated encrypted backups with a tested restore, audit logging. 5. Self-serve signup and billing: Stripe with UK Bacs Direct Debit, 30-day trial, webhook-driven lifecycle, idempotent provisioning (zero-touch signup is an acceptance gate), VAT via Stripe Tax. 6. Companies House multi-tenant (per-tenant keys plus a shared cache). 7. HMRC Making Tax Digital, sequenced last: Developer Hub, OAuth agent authorisation across many firms, fraud-prevention headers, VAT filing. A detailed step-by-step build plan and a written requirements document govern the build. You work on your own copy with supplied dummy data - the live system and real client data never enter your environment. All accounts, code and IP belong to us. Final payment is against the acceptance gates. PROCESS - READ BEFORE APPLYING 1. Apply with the four items below. 2. Shortlisted applicants complete a small paid trial, the same for every candidate. One self-contained, dummy data supplied - it tests database-level tenant isolation and an idempotent signup, the make-or-break parts of this job. 3. Trial passed: NDA, then you receive the full sanitised codebase and detailed plan, and confirm your quote against the real code. 4. Hire, milestones agreed, build. Do not ask for the codebase, a data sample or "a real slice to migrate" before the NDA - the answer is no. INCLUDE IN YOUR PROPOSAL (applications without all four are declined) 1. A multi-tenant SaaS you built on Postgres with row-level security - what it does and your role. 2. Your Stripe subscription billing experience - Bacs Direct Debit specifically, if any. 3. Any HMRC MTD or Companies House API work. We will provide clear guidance. 4. Your indicative price against the seven scope items, key assumptions, and a realistic timeline. SCREENING QUESTIONS 1. Have you shipped row-level security in Postgres to production? Describe the tenant-context mechanism you used in one sentence. 2. In Stripe, why must subscription state come from webhooks rather than the browser redirect? 3. Have you integrated any HMRC API? (Yes/No - not a disqualifier, but tell us.) 4. Are you available for a milestone-based fixed-price engagement starting within two weeks?