Service · Integrations
API Integration Services
Payments, CRMs, and clinical systems wired together so the data still reconciles.
Integration work is where products quietly lose money: a duplicated webhook charges twice, a CRM sync drops a field, a partial failure leaves two systems telling different stories. I have shipped Stripe billing across five products, a HubSpot integration used by 50+ reps, and an HL7 gateway.
An integration is not finished when the happy path returns 200. It is finished when a duplicate webhook, a timeout, and a half-applied write all leave your data correct.
TL;DR
- Stripe integrations across five products, including Stripe Connect creator payouts and automated payouts on a 2,000-booking marketplace.
- HubSpot CRM integration in production: 50+ reps, 10 hours saved per rep weekly.
- Event-sourced ledger with 31 event types and a 6-state escrow machine, with 248 passing tests.
- HL7/FHIR interoperability in a hospital network: 200+ monitors, 10,000+ messages a day, 99% delivery.
The challenge
Integrations get written for the demo and maintained by nobody. The webhook handler assumes one delivery. The sync assumes the third party is up. Reconciliation does not exist, so a mismatch has no event log to explain it.
What I build
Payment Integrations
Stripe, Stripe Connect, and PayPal — checkout, subscriptions, payouts, disputes
CRM Integrations
HubSpot in production: object sync, rate-limited batching, native write-back
Healthcare Interoperability
HL7 and FHIR routing, validation, and HIPAA-conscious patient data
Third-Party & Registry APIs
Rate-limited sources ingested on schedules, with caching and backoff
Webhooks & Event Plumbing
Signature verification, idempotent handlers, replay tooling, and queues
Ledgers & Reconciliation
Event-sourced records, escrow state machines, and durable audit trails
What does a Stripe integration involve beyond taking a payment?
Charging a card is the small part. Production work means idempotency keys so a retried request never double-charges, webhook handlers that survive duplicate and out-of-order delivery, a local record of every state change, and reconciliation between Stripe's numbers and yours.
The receipts vary: a scam detection SaaS running Stripe alongside PayPal, an SMB loyalty platform that has processed $20K, and a UAE marketplace paying providers automatically across 2,000 bookings.
How do you integrate a CRM like HubSpot with an AI feature?
Start from the rep's existing workflow rather than the model. Sync only the objects the feature needs, write results back as native CRM records, batch and queue calls to respect rate limits, and keep every AI-generated action reversible by a human.
That is how Chasr works: GPT-4 follow-up assistance layered onto HubSpot instead of asking a sales team to change CRMs. Salesforce is capability here, not a receipt.
How do you stop two systems drifting out of sync?
Name one system of record per field, make every write idempotent, and make every sync replayable. Prefer events over polling where the source supports webhooks. Where money is involved, derive balances from an immutable event stream, not a stored number.
The strongest example: an SEC Reg CF crowdfunding backend where balances are never stored — they are derived from an event-sourced ledger with 31 event types across 28 Prisma models.
Can you integrate legacy, clinical, or registry systems?
Yes. Older systems rarely hand you a clean REST API — you get HL7 messages, flat files, SOAP envelopes, or a rate-limited registry endpoint. The engineering is the same: a translation layer, strict validation at the boundary, retries, and dead-letter handling.
OpenConnect is the clinical case: an HL7 gateway inside hospital infrastructure ingesting from 200+ patient monitors. A Belgian M&A marketplace integrates 4 registry APIs.
Build it, buy a connector, or run it on an iPaaS
Qualitative trade-offs, not benchmarks.
| Factor | Custom-built | Off-the-shelf connector | iPaaS |
|---|---|---|---|
| Fit to your data model | Exact | Whatever the vendor mapped | Within node limits |
| Partial failures | You design recovery | Whatever shipped | Your error workflow |
| Ongoing cost | Your maintenance time | Subscription per connection | Per execution or task |
| Best when | Money or compliance | Standard flow, popular tools | Many apps, changing logic |
Tech stack
Which of my builds proves this
Named honestly: HubSpot is the only CRM I have shipped, so Salesforce is capability rather than a receipt, and calendar integrations have no case study behind them.
Chasr — AI SalesTech Platform
GPT-4 follow-up assistance wired into HubSpot — 50+ reps, 10 hours saved per rep weekly.
Read case study →SEC Reg CF Crowdfunding Backend
Event-sourced ledger with 31 event types, a 6-state escrow machine, and 248 passing tests.
Read case study →HomeBrigadier — UAE Marketplace
Stripe payments with automated provider payouts across 2,000 bookings.
Read case study →SaaS Backend Platform — Queues, Caching, Retries
The plumbing this page is about, on Node and Deno: 57 hours, a 5.0 rating, and a SaaS client who wrote “by far the best developer I have worked with.”
Read case study →How we work
Most MVPs ship in 3–6 weeks; complex platforms are scoped individually once the requirements are clear.
Intro Call
A 30-minute conversation about your project, goals, and timeline. No commitment either way.
Scoped Proposal
A written scope, architecture outline, and quote. I respond to every message within 24 hours.
Weekly Demos
You see working software every week, with written progress updates in between. No black boxes.
Ship & Handover
Deployment, documentation, and a clean handover — you own everything I build.
Compliance & standards
Frequently asked questions
Can you make our Stripe integration handle refunds and disputes properly?
Do you integrate Salesforce?
How do you handle third-party APIs that are slow or unreliable?
Can you work with HL7, FHIR, or other healthcare systems?
What does an integration project cost and how long does it take?
Ready to start?
Book a free 30-minute call. No sales pitch — just a direct conversation about your project.
Book Free CallOr email: contact@waseemahmad.dev