Senior Full-Stack Developer: Multi-Tenant SaaS on Base44 (Scaling + Ongoing Support Retainer)

I run a software company with a live multi-tenant B2B SaaS built on Base44 (React frontend, managed backend with Deno functions, row-level security, background job queue). The product serves local-business clients across regulated industries and is in active growth. The architecture is already built and tested: tenant isolation with RLS, server-side provisioning, a job engine with retries and dead-lettering, LLM content generation, and third-party integrations (DataForSEO, social publishing API). I am looking for one reliable senior developer to help scale it properly and then stay on for ongoing support. Phase 1: - Performance and scale hardening: query aggregation, job table archival, queue throughput - Extending existing patterns: new entities, new job handlers, new client-facing pages that follow the established design system - Porting approved UI designs from a sandbox app into the production codebase - Strengthening test and verification routines (we re-run tenant isolation checks after every service-role change; you would maintain that discipline) Phase 2 (ongoing retainer, 5 to 15 hours per month): - Bug fixes and small features - Monitoring job queue health and integration failures - Being reachable for production issues within one business day You are a fit if: - You have shipped and maintained at least one real multi-tenant SaaS (please describe the tenancy model you used and one isolation mistake you have seen or made) - You are strong with React, TypeScript or modern JS, and backend data modeling - You have worked with row-level security (Supabase, Postgres RLS, or equivalent) and background job patterns (queues, idempotency, retries) - You write clear async updates without being chased, and you flag risks before acting on them - Experience with Base44, Lovable, or Bolt is a bonus, not a requirement; the platform is learnable in days if the fundamentals are there How we will work: - Everything runs through the existing repo conventions: schema changes only through entity files, checkpoints before risky changes, isolation tests re-run after any service-role code - Paid trial task first (2 to 4 hours, scoped, real): if it goes well, we move to Phase 1 - Work-for-hire with full IP assignment and an NDA; you will sign before repo access To apply, answer these four questions (applications without them are skipped): 1. Describe a multi-tenant system you built or maintained: what enforced isolation, and how did you test it? 2. What is the failure mode of a job queue without idempotency keys? Two or three sentences. 3. Have you worked inside a managed platform (Base44, Supabase, Firebase, Lovable)? What did you like and dislike about the constraints? 4. What is your hourly rate and realistic weekly availability for the next two months? Start your reply with the word "rhythm" so I know you read this.