Freelance senior full-stack engineer. AI products, payment systems and Web3 platforms, built end to end.

Directly. The contract and invoices are with me. If your team prefers a platform for escrow and paperwork, Upwork works as well.

Yes. I work under your brand and in your tools (repo, Slack, standups), client-facing only if you want me to be. The contract and invoices are with the agency, and non-solicit terms go in the contract.

Yes. I start with an eval set built from your real user questions, put the retrieval or agent behind a feature flag in your existing Next.js or Node app, and track cost per request from day one, so the feature can be measured before it is switched on for everyone.

Yes. The rails I have shipped in production are USDC on Base with a dedicated wallet per invoice, gasless transfers through a relayer, fiat on and off ramps through Bridge, Coinbase and Stripe, and Lightning. In an existing product it usually starts as one extra payment method next to your current checkout, with every provider webhook idempotent and reconciled against on-chain balances. CashTap is the reference build.

Yes. A lot of what I build is plain product work: dashboards, onboarding, admin tools and APIs in React, Next.js and Node.js with Postgres, MongoDB or DynamoDB behind them. Trade Bridge is a marketplace I built and maintain on a retainer, and the Sailor RT4822 simulator is a React app I built and deployed for a client.

None by default. The model call sits behind a small adapter, the same pattern I use for payment providers, so OpenAI, Anthropic or an open model can be swapped on cost or data terms without a rewrite.

An eval set from real queries that runs on every change, retrieval that returns its sources so answers can be checked, per-tenant token limits, caching of repeated requests, and a cost view per feature so nobody is surprised by the bill.

Yes. Send yours for review, or I can provide a standard mutual NDA.

Your users' data stays in your accounts and infrastructure. Repositories, cloud accounts and API keys are in your organization from day one, and I sign your data processing agreement when you need one. In regulated builds I keep identity data separate from application data, and I do not copy production data outside your infrastructure.

You do, once the work is paid in full. Repositories are created in your organization from day one, or transferred at handover. The contract states this in writing.

I am in Pakistan (UTC+5), which overlaps most of the European working day. With US teams I work async and schedule calls in the US morning.

Fixed price for scoped builds, a monthly fee for retainers, and an hourly or day rate for contract roles. Everything is written down before work starts. Invoiced per milestone or monthly, paid by bank transfer or Payoneer, or through Upwork escrow if you prefer.

No, I do not audit contracts myself. I write and test them with Foundry, and contracts I wrote have been through an external audit before mainnet. For a formal audit I recommend an audit firm and prepare the codebase so the audit is short and clean.

Yes. The first step is a short review with a written list of risks, quick wins and what I would change first.