DENYS Z.

Full-Stack SaaS Developer, Next.js, React, TypeScript, PostgreSQL

Multi-tenant SaaS developer specializing in Next.js, React, TypeScript, Supabase and Stripe. I build production-grade SaaS platforms and web applications - from an empty repo to deployed and in use. I've shipped multiple production multi-tenant SaaS platforms and full-stack web apps, all with 100% Job Success on Upwork. The hard part of multi-tenant SaaS is usually not the features. It's making sure tenant A can never see tenant B's data, even by accident. I enforce that at the database level with Supabase Row-Level Security - not with app code you have to trust to get right every time. If you have an idea but no working app yet, I take it from empty repo to shipped: auth, Stripe billing, role-based access, and an admin panel to run it all. If you already have something half-built or AI-generated (Lovable / Cursor / v0) that needs fixing or scaling, I do that too. WHAT I BUILD - Full-stack SaaS platforms & MVPs - Next.js (App Router), React, TypeScript - Multi-tenant SaaS - isolated tenant workspaces, per-tenant data isolation with Row-Level Security (RLS) - B2B SaaS - self-service onboarding, role-based access control (RBAC), Stripe subscription billing - Admin dashboards & internal tools - user management, verification workflows, data tables - Custom CRM systems - lead management, pipelines, client portals - API & AI integrations - REST APIs, webhooks, OpenAI / LLM features - Data dashboards - real-time analytics, charts, automated reporting HOW I ARCHITECT MULTI-TENANT SAAS Most clients need the same thing: one codebase serving many clients, with strict data separation. Here's how I build it: - Per-tenant data isolation at the database level with Supabase Row-Level Security (RLS) - FORCE RLS and column-level access, so isolation never depends on app code being perfect - Layered role-based access control (RBAC) - platform, organization, and project permission levels - Object-level authorization on every endpoint - each request is checked against IDOR / broken access control (BOLA), so no user can reach another tenant's data by guessing an ID - Stripe subscription billing - plans, upgrades, usage limits per tenant - Self-service tenant onboarding - clients sign up and get a working workspace on day one - MFA/TOTP with step-up auth, secure session management and revocation - Immutable audit logs, hashed tokens/secrets, rate limiting and security headers - audit-ready, SOC2-aligned controls - Admin panel to manage tenants, users, verification queues and analytics from one dashboard RECENT WORK 1. Padel club platform - Multi-tenant SaaS for padel clubs - members, matches, rankings and sponsor banners, each club in its own isolated workspace. Supabase Row-Level Security for strict per-tenant isolation, self-service onboarding, one codebase serving many clubs. 2. Field operations B2B SaaS - Multi-tenant platform for field documents, dynamic forms and QA workflows. Layered RBAC with 13 roles across 3 permission levels, RLS-backed tenant isolation, MFA at the middleware layer. Custom formula engine, versioned form templates, server-side PDF generation, Stripe subscription billing, secure external document sharing. 100+ DB migrations, 105+ tests. 3. Real-time marketplace platform - Real-time SaaS marketplace with a full admin suite: user management, verification workflows, analytics, messaging and support tickets. Custom SQL functions for sub-second data aggregation and live updates across all connected clients. 4. B2B ordering MVP - Mobile-first ordering platform connecting restaurants and suppliers, with separate accounts for each side and an admin dashboard for suppliers, products and orders. Scoped as a lean MVP to validate the business model before scaling. MY STACK Next.js (App Router), React, TypeScript, Node.js, Python. Supabase and PostgreSQL for database and auth. Stripe for payments. Deployed on Vercel and Cloudflare for edge performance. I use Claude Code to ship faster without cutting corners. HOW I WORK 1. Discovery - I map your workflow, define MVP scope and agree on deliverables before any code. 2. Build - clean code, daily updates, working builds from day one. 3. Deploy - production-ready from launch, full ownership of the repo from the first commit. WHY CLIENTS HIRE ME - Security-first: every change is reviewed and pentested for IDOR, broken access control and RLS bypass before it ships - not bolted on after a breach. - 100% Job Success and Top Rated - I care whether the product is solid, not just whether it demoed well. - Full ownership from first commit to deployment. No handoffs, no lock-in. - A real product with auth, payments and admin wired up. Not a demo. - Clean, documented code you can extend, not a quick hack you rewrite in 6 months. Got a multi-tenant SaaS idea, a full-stack web app or an internal tool to build? Send a short description and I'll reply within 2 hours with a scope and timeline - or let's jump on a call. Let's get the ball rolling!