Serving global clients

Senior SaaS & FintechArchitect

I build backends that don't collapse when your Stripe webhooks fire at 3 AM. Payment integrity, multi-tenant isolation, AI pipelines that actually ship. 11 years of production scars, not slide decks.

Assad Ullah Chaudhry. I work with founders who need a system that holds up under real load. Not duct tape.

Available for projects
11+Years in prod
135+Projects shipped
4.97Avg. Rating
6+SaaS Launched

Services

What the engagement
looks like

I help startups design, build, and scale the systems that keep their product running when it actually starts to matter.

  • SaaS Development

    Multi-tenant SaaS platforms with subscription billing, role-based access control, and backend architecture designed to carry real load from day one.

    Multi-tenancySubscriptionsDashboardsRole-based Access
  • Fintech & Payment Systems

    Stripe Connect integration, marketplace payout systems, and subscription billing infrastructure engineered for financial accuracy. Every webhook idempotent. Every failure state handled.

    Stripe ConnectMarketplace PayoutsBillingWebhooks
  • AI Integration & Automation

    Production-grade LLM integration: RAG pipelines, streaming interfaces, and AI automation workflows with proper cost controls, observability, and failure handling built in from the start.

    LLM IntegrationRAG PipelinesAutomationStreaming UI
  • Web & Mobile Development

    Next.js web apps and React Native mobile applications built for speed, SEO, and production scale. SSR/SSG/ISR rendering strategy, 90+ Lighthouse scores, and CI/CD deployment from day one.

    Next.jsReact NativeTypeScriptPerformance
  • Not sure if this fits your project? See who I work with →

Who I Work With

Serious
products only

I work with founders and product teams building for scale. If you're still validating an idea on a spreadsheet, we're not a fit yet. Come back when it's time to build properly.

01

Fintech Founders & SaaS Builders

Stripe Connect architectureIdempotent API designMulti-tenant SaaSSubscription billing infrastructure

You're building a platform where money moves — subscriptions, marketplace payouts, creator earnings — and the billing layer can't be a pile of Stripe calls held together with optimism. I've designed these systems from the object model up: idempotent webhook handlers, Connect onboarding that accounts for KYC edge cases, and multi-tenant data structures where one customer's financial records are physically isolated from another's. The kind of architecture your investors and auditors will want to see.

  • Idempotent billing logic that prevents double-charges when Stripe retries a webhook at 3 AM
  • Multi-tenant schema design with hard data boundaries — not row-level filters that can be misconfigured
  • Stripe Connect onboarding flows that handle KYC failures, account deauthorization, and payout holds explicitly
02

SaaS Teams Carrying Architectural Debt

SaaS performance optimizationNode.js concurrencyArchitectural refactoringCore Web VitalsDatabase query optimization

The system worked fine at 200 users. Now you have 2,000 and things are cracking — slow queries under concurrent load, race conditions in financial workflows that only reproduce in production, a codebase where adding a feature takes three times longer than it should. I've refactored enough of these systems to know what the problems actually are before I open a file. The usual suspects: missing database indexes, no connection pooling, business logic buried in controllers, and a billing integration that was bolted on rather than designed in.

  • Diagnosing and eliminating race conditions in payment and subscription workflows under real concurrency
  • Refactoring monolithic or tangled codebases into a structure that doesn't fight you when requirements change
  • Backend response time and Core Web Vitals improvements with measurable before/after benchmarks
03

Agencies With a Build They Can't Afford to Get Wrong

Fractional CTOSenior technical leadSaaS architecture consultantAI LLM integrationAPI design and orchestration

You've taken on a client project that's technically more complex than your team's usual scope — a SaaS platform with real billing logic, an AI integration that needs to actually work in production, or a fintech product where the payment layer has to be right. You need a senior engineer who can own the backend architecture and make decisions your client's CTO won't question later. I've filled this role before: I work to your delivery schedule, document decisions clearly, and hand off code that your team can maintain without me.

  • Owning backend architecture decisions on high-stakes builds — including the ones clients want to revisit at launch
  • Building and integrating production-grade AI and LLM workflows your team can extend, not just demo
  • Clean, documented handoffs: commented code, architectural decision records, and runbooks your developers can actually follow

Sound like your situation?

Typically responds within 24 hours.

Discuss your project

Case Studies

Selected
Case Studies

01

Corely

Creator Monetization Platform — Stripe Connect, Subscription Billing & Automated Payout System

View Case Study

Most creator monetization tools are either too simplistic (basic payment links with no subscription logic) or too complex (full marketplaces with infrastructure the creator doesn't need). Corely sits in the right place: one creator, one profile, direct audience payments, automatic payouts. The engineering challenge was building a Stripe Connect integration that handles the full financial lifecycle — onboarding, KYC handoff, subscription management, payout routing, and the 2% platform commission — without exposing the creator to any of that complexity on the frontend.

Outcome

Shipped a production-ready platform with fully automated financial operations. No manual payout processing. No reconciliation spreadsheets. The 2% fee model generates platform revenue that scales with creator volume without adding operational overhead — which is the only fee model that makes sense at scale.

Role

Lead Full Stack Engineer. I owned the entire payment architecture: Stripe Connect Express account onboarding, subscription lifecycle management with Stripe Billing, payout routing logic, the 2% commission engine, webhook infrastructure for all payment events, and the creator-facing earnings dashboard.

02

Kodezi

AI-Powered Web IDE & Developer SaaS — 200K Users, Product Hunt Launch of the Month, v1 through v4

View Case Study

Kodezi is not a thin wrapper around an LLM API. It's a full in-browser IDE — Monaco Editor with multi-tab state, diff views, codebase-aware context — with OpenAI integration that understands your actual project, not just the snippet you paste in. I built it from v1 through v4: the initial MVP, KodeziChat with real-time Socket.io streaming, a credits-gated subscription system enforced at the API level, a VS Code extension with native-feeling Webview UI, and separately, an automated system status tracker that replaced manual monitoring entirely. The 200K user milestone and Product Hunt Launch of the Month were outcomes of getting the product architecture right across four iterative versions.

Outcome

200K active users. Product Hunt Launch of the Month (February 2023), Launch of the Week, and two Launch of the Day awards. The platform scaled from a single-developer MVP to a multi-version SaaS with real-time AI, gated premium features, in-editor tooling, and fully automated infrastructure monitoring — without requiring a rewrite of the core architecture between versions.

Role

Core full stack engineer across all four versions. V1: built from scratch — website, Web IDE, backend APIs, Stripe subscriptions. V2: led KodeziChat UI and Socket.io streaming integration, built the VS Code extension Webview UI. V3: contributed to Kodezi Cloud in a team. V4: rebuilt the dashboard, implemented multi-subscription Stripe handling. Built the Auto System Status Tracker independently as a separate deployment.

Process

How a project moves
from idea to production

Structured, not bureaucratic. The goal is a working system, not a methodology.

Phase 01

Product Decomposition and Risk Mapping

Before any code exists, I map your product into its system components: tenant model, data schema, permission layers, and billing logic. The point is to find the architectural decisions that are expensive to reverse and make them correctly the first time. Scaling risks and technical constraints get documented here, not discovered in month four.

Outcome

A written system map covering tenant model, data ownership boundaries, permission layers, and billing logic. Each high-risk architectural decision is flagged and justified before the build begins.

Phase 02

Architecture and Database Design

Full system design: multi-tenant schema strategy covering schema-per-tenant versus row-level security, API contracts, RBAC structure, and third-party integration points. You get a production-grade blueprint with a clear rationale behind every decision. Not just a diagram that looks good in a slide deck.

Outcome

A production-grade architecture document: schema strategy, entity-relationship design, API surface definition, RBAC matrix, and third-party integration contracts. Every decision is documented with its tradeoffs, not just its conclusion.

Phase 03

Schema Review and API Contract Sign-Off

Before the first route gets written, the database schema and API contracts go through a dedicated review pass. This is the cheapest moment to catch a flawed foreign key relationship, a missing index, or an API shape that will make the frontend painful to build. Fixing these in a document costs an hour. Fixing them after the ORM models are wired costs a week.

Outcome

A signed-off schema and API contract that both sides have reviewed and agreed on. Frontend and backend development can start in parallel against a stable contract with no rework caused by late-stage shape changes.

Phase 04

Core Platform Build

Backend-first. Authentication, tenant isolation, billing integration, and the API layer get built and tested before the dashboard goes up. Frontend dashboards and onboarding flows are built on top of a stable, tested core. Not the other way around.

Outcome

A fully functional platform: working authentication, enforced tenant isolation, integrated Stripe billing, tested API layer, and operational dashboards. Every component is integration-tested before it is handed to the next layer.

Phase 05

QA, Load Testing, and Launch

Load testing, edge case coverage, and database query optimization before any production deployment. Infrastructure is provisioned with monitoring, alerting, and runbooks that someone other than me can follow at 2am.

Outcome

A production system with verified performance under load, documented edge case handling, a query-optimized database, active monitoring and alerting, and runbooks for the failure scenarios most likely to occur in the first 90 days.

Tech Stack

Proven tools.
No hype cycles.

I use technologies that have earned their place in production, not the ones that made it to the top of Hacker News last month.

Core Stack

ReactNext.jsNode.jsLaravelAWSStripe

Frontend01

ReactNext.jsTypeScriptTailwind CSSReact QueryGraphQLReduxReact NativeMaterial UI

Backend02

Node.jsExpress.jsLaravelLumenKoa.jsCodeIgniterWordPress

Databases & Storage03

PostgreSQLMySQLMariaDBMongoDBRedisSupabaseFirebaseAWS RDS

Infrastructure & DevOps04

AWS (EC2, S3, SES)VercelDigitalOceanDockerNginxApacheCI/CD PipelinesGithubGitlab
AI

Applied Intelligence Integration

LLM IntegrationAI API IntegrationStreaming InterfacesIntelligent WorkflowsVector Database Integration

Integrating AI into real products using LLM APIs, automation workflows, and scalable data pipelines — built for production, not demos.

Common questions

Straight
Answers.

No vague pricing ranges or diplomatic non-answers. If I don't know something, I'll say so.

Anyone who quotes you a number before reading your requirements is guessing. Simple SaaS platforms start around $10-20K. Fintech platforms with custom billing engines, multi-tenant architecture, and AI integrations are significantly more. I run an architecture phase before either of us commits to a number, because scope discovered late costs three times as much to fix.

A lean MVP takes 5-10 weeks. A full-scale platform with payments, user management, and AI integrations takes 3-5 months. Timelines slip when scope grows mid-project. That is why I invest time upfront in architecture and planning before a single line of production code is written.

Both. An MVP built on the wrong architecture becomes technical debt fast. I build MVPs with the right foundations so scaling does not require a rewrite. If you need a throwaway prototype, I am not the right hire.

Yes. I have refactored legacy systems into performant architectures, eliminated race conditions in financial workflows, and migrated codebases that were actively costing companies money in downtime and support tickets. I start with an architecture audit so we both know exactly what we are working with before touching anything.

Mostly startups and high-growth product teams. Company size is not the filter. Seriousness is. I work with teams who understand that architecture decisions made in month one still matter in month eighteen.

I implement designs and advise on UX patterns for technical interfaces. I am not a visual designer. If your project needs bespoke brand identity or motion design, you need a dedicated designer in the process. I will tell you that honestly upfront rather than after the first invoice.

Yes. LLM APIs, RAG pipelines, streaming interfaces, automation workflows. I integrate AI where it solves a real problem and the existing architecture can actually support it, not as a feature checkbox to put on a pitch deck.

React, Next.js, Node.js, Laravel, AWS, Stripe, PostgreSQL, MongoDB, Redis, Docker, and LLM APIs including OpenAI and Anthropic. I use what the project actually needs, not whatever I learned most recently.

Client Record

11+ Years Building Production Systems
Every project delivered. No exceptions.

Complex Systems Engineering

Assad is honest, reliable and trustworthy. I had quite a complicated bit of coding that was required and Assad made light work of it. The project was scheduled to be completed within 3 days but Assad worked all through the night to get my work complete in 1 day. An absolute pleasure to work with and highly recommended.

Nab Z.

🇬🇧 United Kingdom

Verified Client
SaaS Development

Incredible attention to detail and willing to go above and beyond the requirements to meet the needs of the project. I am very lucky to have found Assad and can't wait to work with him again for Phase 2 of my project.

Dylan G.

🇺🇸 United States

Verified Client
Web & Mobile Development

I hired this seller again for a mobile app. One of our in-house developers was tricking us but Assad was so transparent. The communication, the quality of work everything was excellent and he was so quick. We will hire Assad for all our future projects.

Iftikhar A.

🇵🇰 Pakistan

Verified Client
Web & Mobile Development

Assad was an outstanding developer. I had trouble in the past with developers but working with Assad was completely different experience. Great communication, great work and best developer I ever worked with. I 100% recommend him.

Iftikhar A.

🇵🇰 Pakistan

Verified Client
SaaS Development

This was the first time I used Fiverr to build a dashboard and Assad Ullah exceeded my expectations. Not only did I get a robust site but the level of design went beyond cookie cutter to something that feels premium and customized!

Flex S.

🇵🇰 Pakistan

Verified Client
Fintech Systems

Very competent, got straight to the diagnosis of the issue and a prompt resolution to my cart issue. I will definitely be working with him again. Response time: excellent! Don't want to recommend so I can keep him to myself.

Mobi Z.

🇺🇸 United States

Verified Client
Web & Mobile Development

Exceptional job. There was an issue with the app and background notifications were not working. Assad literally took a few minutes to fix that all. I am very impressed by this developer and I will be hiring him for future projects.

Domenion B.

🇧🇭 Bahrain

Verified Client
SaaS Development

AMAZING WORK!! He asked what I was looking for and delivered more than I expected. I definitely recommend his services to anyone who is looking for classic, detailed work.

Domenion B.

🇧🇭 Bahrain

Verified Client
Web & Mobile Development

I hired them to develop a React Native authentication screen, and the results were outstanding. They not only delivered the project ahead of schedule but also paid attention to every detail, ensuring the design was sleek, functional, and easy to integrate into my app. Their expertise in React Native is evident.

Navan J.

🇧🇭 Bahrain

Verified Client
Web & Mobile Development

From start to finish, they demonstrated exceptional skills, professionalism, and a deep understanding of both frontend and backend development. The project was completed on time, and the quality of the work exceeded my expectations.

Navan J.

🇧🇭 Bahrain

Verified Client
Web & Mobile Development

Working with Assad was above expectations. He is very clear and fast in communication, thinks along, and most importantly delivers very high quality. Will definitely use his services for more projects.

Steven MC.

🇳🇱 Netherlands

Verified Client
SaaS Development

Assad didn't just write code, he thought through the architecture before the first line was typed. He joined us for the initial MVP and performed so well that we brought him on as a founding full-stack engineer. Over four major versions, he shipped the AI-powered IDE, the real-time KodeziChat experience, the VS Code extension, and a completely automated system status tracker, all while we scaled to 200,000 users and won Product Hunt Launch of the Month.

Ishraq K.

🇺🇸 United States

Verified Client
Web & Mobile Development

He was professional, communicative, and took the time to understand my needs. The project was completed on time, within budget, and the quality was outstanding. The website functions perfectly, and his attention to detail exceeded my expectations.

Rodger D.

🇵🇰 Pakistan

Verified Client
SaaS Development

Working with Assad was an amazing experience! He delivered high-quality work on time and exceeded my expectations. Great communication, professional attitude, and top-notch skills. Highly recommend - 5 stars all the way.

Rodger D.

🇵🇰 Pakistan

Verified Client
Web & Mobile Development

This seller is an absolute superstar! He dedicates all his time and effort to your project, working tirelessly around the clock to ensure its success. I often have to remind him to take time for himself because he makes my project such a top priority. His communication is fantastic, and his work ethic is unmatched.

Sunny P.

🇵🇰 Pakistan

Verified Client
Web & Mobile Development

Assad is great, he jumps in when and where it is necessary to help get projects finished correctly and on time.

Sunny P.

🇵🇰 Pakistan

Verified Client
SaaS Development

This seller is such an amazing talent. Amazing job done with very little information provided. Great problem solver. Would love to hire him and his team again and again.

M. Mohsin

🇵🇰 Pakistan

Verified Client
Web & Mobile Development

Assad is very professional in the way he works. He does a good job and I am always impressed by the quality of the final work.

Gabriel Y.

🇨🇦 Canada

Verified Client
SaaS Development

Very professional and promising seller. If you got a complex project, assadullahch will bring it to life. If you want speed, contact assadullahch. If you want quality, contact assadullahch.

Aimen C.

🇵🇰 Pakistan

Verified Client
SaaS Development

I have tried Assadullahch on more than 10 projects and he always produces quality. Very patient and very professional. He is the programmer that you want in your team.

Aimen C.

🇵🇰 Pakistan

Verified Client
SaaS Development

He is a real pro and understands things very quickly. I did not even explain my full requirements and he did it way more than my expectations.

Aimen C.

🇵🇰 Pakistan

Verified Client
Web & Mobile Development

This seller is a very professional individual and provided above and beyond what was requested even when there were delays from my side. Very much hope to work with them again.

Ralph C.

🇺🇸 United States

Verified Client
SaaS Development

I design websites, but when the job is too technical I contact Assadullahch. This is the second time he has helped me with a tough and highly technical job using his vast knowledge, skill and expertise. He is always professional and patient to make sure you're satisfied.

Raymond O.

🇳🇬 Nigeria

Verified Client
Web & Mobile Development

Assad is awesome, very professional, patient and skillful. I am very happy with the job done and highly recommend him.

Ecer T.

🇳🇬 Nigeria

Verified Client
Fintech Systems

Assad was able to complete a project and fix all our problems and bugs and communicate very clearly with us. We will be hiring him for all our future projects!

Tom D.

🇺🇸 United States

Verified Client
Web & Mobile Development

Assad and team did an amazing job for us. We tried many developers who did not fulfil our requirements. These guys took on that job and delivered beyond expectations. Highly recommended.

Mo Ali U.

🇵🇰 Pakistan

Verified Client
Web & Mobile Development

This is the second time I work with assadullahch and again, the work is done properly with care and the timing is great. I would recommend assadullahch to anybody who needs a real developer to bring your project to life.

Joe B.

🇬🇧 United Kingdom

Verified Client
Web & Mobile Development

Very patient, skilled and honest. That is the programmer you need in your team.

Joe B.

🇬🇧 United Kingdom

Verified Client
Web & Mobile Development

Very professional and detail oriented. Assad did everything we asked quickly even if it wasn't in the preliminary instructions. It's great to have a competent person who knows what they're doing.

Nab Z.

🇬🇧 United Kingdom

Verified Client
Web & Mobile Development

Exceptional developer. The communication was very clear and he did a tremendous job. I will be hiring him for all of our future projects.

S. Samir

🇵🇰 Pakistan

Verified Client
SaaS Development

Such an amazing developer. He is super talented and capable of handling complex requirements with ease. Highly recommended.

Jordan R.

🇵🇰 Pakistan

Verified Client
Web & Mobile Development

Fast. Patient. Understanding. While trying to resolve my gig we ran into technical challenges that caused us both frustrations. Nothing he nor I had control over. The gig was still delivered as promised and with graciousness.

P. Boomer

🇺🇸 United States

Verified Client
Web & Mobile Development

Assad is great to work with and an excellent communicator so language wasn't an issue at all. He's also displayed great problem solving skills.

Seann P.

🇦🇺 Australia

Verified Client
Web & Mobile Development

Absolutely incredible work! I will continue to work with him. My first pick ALWAYS.

Rebecca H.

🇺🇸 United States

Verified Client
Web & Mobile Development

Excellent seller. Really over-delivered on a tricky custom order. Will work with him again.

Josh H.

🇺🇸 United States

Verified Client
Fintech Systems

He delivered a seamless experience: a custom Stripe subscription flow with monthly and yearly options, an application questionnaire that feeds into ActiveCampaign, automated payment emails via AWS SES, and a premium events section. The whole pipeline from inquiry to paying member now runs automatically. It's a platform that matches the quality of the movement Jimmy has built.

Brett H.

🇺🇸 United States

Verified Client
Web & Mobile Development

He architected a real-time feed, group and one-on-one chat, admin-managed training playlists, and role-based access control, all powered by Socket.io so everything updates live. The React Native iOS app mirrors the web experience completely. Engagement took off the moment we launched.

Brett H.

🇺🇸 United States

Verified Client

Start a Project

If the system needs
to hold, let's talk.

I work with founders and teams building SaaS platforms, fintech infrastructure, and AI-integrated products. If you need something reliable and are willing to invest in building it properly, I'm available for architecture audits and project work.

Project Fit

  • SaaS platforms & product engineering
  • AI integrations
  • Backend systems
  • Fintech infrastructure
Request Project Discussion →

Typically responds within 24 hours