You will get Build a Modern, Scalable API with NestJS + PostgreSQL
Top Rated
Project details
Need a secure, scalable backend API that just works — fast and with clean code?
I'm a Top-Rated Plus full-stack developer with 14+ years of experience building production-grade APIs using NestJS, PostgreSQL, and TypeScript. I’ll build your API with modern patterns like modular architecture, repository layers, DTO validation, and JWT authentication — ready for production and future scale.
Perfect for:
SaaS platforms (admin dashboards, booking systems, CRMs)
Mobile + Web apps needing a robust backend
MVPs that need a clean start without tech debt
I'm a Top-Rated Plus full-stack developer with 14+ years of experience building production-grade APIs using NestJS, PostgreSQL, and TypeScript. I’ll build your API with modern patterns like modular architecture, repository layers, DTO validation, and JWT authentication — ready for production and future scale.
Perfect for:
SaaS platforms (admin dashboards, booking systems, CRMs)
Mobile + Web apps needing a robust backend
MVPs that need a clean start without tech debt
Programming Languages
TypeScriptWhat's included
| Service Tiers |
Starter
$500
|
Standard
$900
|
Advanced
$1,500
|
|---|---|---|---|
| Delivery Time | 3 days | 5 days | 7 days |
Number of Revisions | 3 | 3 | 3 |
Design Customization | - | - | - |
Content Upload | - | - | - |
Responsive Design | - | - | - |
Source Code |
Optional add-ons
You can add these on the next page.
Fast Delivery
+$1,000 - $2,000
70 reviews
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JO
Jeremiah O.
Jun 2, 2026
Backend Developer Needed for Next.js AI Chatbot Website
Yasser is one of the most hard-working engineers I've worked with. He consistently goes above and beyond to get things done. High agency, fully owns his work, and pushes until the problem is actually solved.
He's a fast learner who takes instruction and feedback exceptionally well, and he's grown a lot as a result, particularly in picking up agentic tools quickly and effectively. His years of experience really show in top-level decision-making around system architecture and software design and code quality.
I loved working with him and he's very knowledgeable on several software engineering concepts and fields. He's a strong, reliable engineer, a man of high integrity, and genuinely honest. It's been a pleasure working with him, and I'd happily continue to.
He's a fast learner who takes instruction and feedback exceptionally well, and he's grown a lot as a result, particularly in picking up agentic tools quickly and effectively. His years of experience really show in top-level decision-making around system architecture and software design and code quality.
I loved working with him and he's very knowledgeable on several software engineering concepts and fields. He's a strong, reliable engineer, a man of high integrity, and genuinely honest. It's been a pleasure working with him, and I'd happily continue to.
TV
Temur V.
May 20, 2026
[URGENT] Lead AI Engineer: Sub-500ms AI Cashier MVP (WebRTC, LiveKit, LLM)
Yasser did an excellent job building our initial AI avatar MVP. He was responsive, communicated clearly, and delivered exactly what we needed for our early validation phase. Highly recommend him for quick and efficient prototyping.
ZA
Zakaria A.
Apr 27, 2026
Vet Management System SaaS Application Development
Yasser did an excellent job building a solid SaaS foundation for the medical platform, with a clear structure that can now support future features, scaling, and continuous improvement.
SL
Sam L.
Mar 27, 2026
AI-first senior engineer to debug and stabilize a production `Dagster` OCR pipeline
The initial assessment work was completed separately, but the main milestone was outcome-based and was not achieved. The project required a reliable, validated end-to-end OCR pipeline, and that result was not delivered despite repeated discussions during the engagement about lack of concrete progress. I therefore could not approve the final milestone.
NG
Noah G.
Mar 20, 2026
Stitch Contractor Estimator Web App (Next.js + Supabase + Stripe + PDF) – MVP Build
It was a pleasure working with Yasser. He took the time to understand the project well, was patient throughout the process, and showed strong knowledge in the technical side of the build. He helped me get the MVP to the finish line and was calm and professional when working through issues. I’m thankful for his help and would gladly work with him again
About Yasser
Senior AI & Full-Stack Architect | LLM Systems, SaaS, Fintech
95%
Job Success
Queluz, Portugal - 6:13 pm local time
Most engagements start with a fixed-price design phase that defines architecture, scope and roadmap, then convert into fixed milestones, so delivery stays structured and budget predictable. Rate $125-150/hr depending on complexity; most work is delivered as fixed-price milestones.
What I specialise in:
AI/LLM systems - RAG pipelines, multi-tenant AI assistants, agent orchestration, Claude/OpenAI integrations, structured outputs, eval pipelines.
SaaS platforms - multi-tenant architecture, subscription billing, RBAC, admin backends, scalable APIs across web and mobile.
Fintech/compliance - ACH, Stripe Connect, idempotent payment webhooks, audit logging, GDPR-compliant data.
Govtech/regulated - transparency platforms, donor-funded compliance, multi-language reporting.
Blockchain/Web3 - Solana smart contracts, SPL tokens, DeFi integrations.
Selected results (live demos and links in the Portfolio section):
Minerva (active production) - multi-tenant AI assistant platform architected end to end: organizations upload document libraries and deploy embeddable chatbots on their own knowledge base. Hybrid retrieval (BM25 + dense vector + semantic), Entra ID + RBAC + MFA, full tenant isolation, golden-query eval harness in CI. NestJS, Next.js, Azure OpenAI.
Diginak.ai (active production, lead architect) - logistics document automation that auto-processes ~78% of inbound PDF/CSV/Excel with zero human touch; the remainder routes to human review with confidence scores. Claude API + tool use, state-machine workflow engine, retry/idempotency, 850+ automated tests. NestJS, PostgreSQL.
Walletta AI Cashier (concluded May 2026, 5-star) - real-time voice agent with sub-500ms perceived latency. Claude + GPT-4o orchestration, structured tool calls with confidence-scored routing, persistent WebSocket, retry with circuit breaker. LiveKit, Deepgram, ElevenLabs, NestJS.
Damen Capital Portal (concluded May 2026, 5-star) - loan-servicing portal for a private lender with the full ACH lifecycle: tokenization, NACHA returns R01-R85, HMAC-verified idempotent webhooks, append-only audit log, OAuth 2.0 + RBAC, scheduled reconciliation. NestJS + Fastify, Supabase.
PulseYourBiz (active production) - all-in-one SaaS for service providers: bookings, payments, invoicing, CRM, analytics. Five-app Turborepo monorepo, Stripe Connect payouts, idempotent webhooks, React Native mobile. Docker + GitHub Actions.
ProveYourImpact (production) - multi-tenant governance/compliance platform for donor-funded projects in PALOP countries: 20 API modules, 9-role RBAC, configurable workflow engine, audit log, EU/UNDP/World Bank report generators in four languages. NestJS, Next.js, PostgreSQL + RLS.
Also shipped: no-code Solana token/DeFi platform with 1,500+ users (SwapForge), offline-first clinical decision support for underserved regions (ExtendYourClinic), multi-tenant VetSaaS with PostgreSQL RLS isolation (acti.vet), React Native apps live on both app stores (ForroAI).
Tech stack:
Backend: Node.js, NestJS, Python, FastAPI, REST, GraphQL. Frontend: React, Next.js, React Native, Expo, TypeScript, Tailwind. AI: Claude, OpenAI, RAG, pgvector, Azure Cognitive Search, structured outputs (Zod/Pydantic), prompt caching, tool use, eval harnesses in CI. Cloud: Azure (Functions, OpenAI, Entra ID, Key Vault, App Insights, Bicep IaC), AWS, GCP, Docker, GitHub Actions. Databases: PostgreSQL, MongoDB, Redis, Supabase, RLS tenant isolation. Blockchain: Solana, Anchor, SPL, Jupiter, Solidity, EVM.
Working model: 25-30 hrs/week across a small number of parallel engagements. Best fit when the product needs architectural ownership - not a fit for quick fixes or one-off tasks.
Steps for completing your project
After purchasing the project, send requirements so Yasser can start the project.
Delivery time starts when Yasser receives requirements from you.
Yasser works on your project following the steps below.
Revisions may occur after the delivery date.
Project Kickoff & Requirements Review
Review client requirements, clarify endpoints, models, and expected behavior. Deliver a short API spec for confirmation.
API Design & Initial Setup
Set up project structure with NestJS or Express. Configure base routes, environment, and database models.