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Malik Hamza Shabbir
Backend

API & Payment Integration

I build production API integration services for SaaS and product teams, shipping Stripe payments, webhooks, and third-party integrations remotely.

Send your project brief Last updated June 10, 2026
In short

API integration services connect your product to payment providers, third-party APIs, and your own data layer without breaking in production. I build Stripe subscriptions, Connect, and webhook flows, plus REST and GraphQL APIs on Node and Python. I handle idempotency, retries, and signature checks so money and data stay correct.

What you get

Stripe integrations: subscriptions, metered billing, Stripe Connect, customer portal, and the full checkout flow
Signed, idempotent webhook handlers that verify signatures and survive retries without double-charging
REST and GraphQL APIs built on Node, Express, and Python, typed end to end with TypeScript
Multi-tenant SaaS backends with tenant isolation on PostgreSQL, MySQL, or MongoDB
Third-party API integrations: OAuth flows, rate-limit handling, pagination, and background jobs
Data layer work with PostgreSQL, MySQL, MongoDB, and Redis for caching and queues
Reconciliation logic so your database and Stripe records always agree
Clear API docs, Postman or OpenAPI specs, and a test suite so your team can maintain it

How I work

  1. 01

    Short scoping call

    We talk through your API, payment flow, or integration. I ask about volume, edge cases, and existing code, then send a fixed price and timeline.

  2. 02

    Build and integrate

    I build the endpoints, Stripe flows, or webhook handlers with idempotency and signature checks. I test against Stripe test mode and sandbox APIs as I go.

  3. 03

    Test and document

    I write integration tests, verify webhook retries and edge cases, and hand over OpenAPI or Postman docs so your team can maintain everything.

  4. 04

    Ship and support

    I deploy with you, watch the first live events and payments, and fix anything that surfaces. I stay available for a short support window after launch.

Ways to work together

Stripe billing setup, 1 to 2 weeks, fixed price

I wire up Stripe subscriptions, the customer portal, and signed webhook handlers. You get plans, upgrades, cancellations, and idempotent event handling that stays in sync with your database.

Third-party API integration, fixed-price sprint

I connect your product to an external API with OAuth, retries, rate-limit handling, and background jobs. Scoped after a short call so you get a firm price and timeline.

REST or GraphQL API build, scoped engagement

I design and build a typed API on Node or Python with auth, validation, and tests. Includes OpenAPI docs so your team can extend it without me.

Multi-tenant SaaS backend, project-based

I build the backend and data layer for a multi-tenant SaaS, with tenant isolation, role-based access, and PostgreSQL or MongoDB. Includes webhooks and billing hooks where needed.

Tech I use for this

StripeNode.jsExpressPythonTypeScriptGraphQLRESTPostgreSQLMySQLMongoDBRedisOpenAPIn8nOAuth 2.0

Common questions

Q.How much does it cost to build a Stripe integration or API?

Integration work is usually a fast fixed-price engagement. Most Stripe billing setups and single API integrations land in a few thousand dollars, depending on edge cases and volume. Larger multi-tenant backends cost more. I scope your exact needs on a short call, then send one fixed quote with a timeline before any work starts.

Q.Can you set up Stripe subscriptions and webhooks correctly?

Yes. I build Stripe subscriptions, metered billing, Connect, and the customer portal, plus webhook handlers that verify signatures and stay idempotent. That means retries never double-charge and your database stays in sync with Stripe. I test every flow in Stripe test mode before going live, including upgrades, cancellations, and failed payments.

Q.Do you build REST and GraphQL APIs, not just integrations?

Yes. I design and build REST and GraphQL APIs on Node, Express, and Python, typed end to end with TypeScript. Each API ships with auth, input validation, rate limiting, tests, and OpenAPI docs. I focus on APIs your team can read and extend after I hand them over, not a black box only I understand.

Q.Can you build a multi-tenant SaaS backend?

Yes. I build multi-tenant SaaS backends with tenant isolation, role-based access, and PostgreSQL, MySQL, or MongoDB. I add Redis for caching and queues, plus Stripe billing hooks and webhooks where you need them. I am a solo mid-level engineer, so I am honest about scope and keep the data model clean and maintainable.

Q.How do you handle webhook reliability and failed payments?

I make every webhook handler idempotent and signature-verified, so Stripe or third-party retries process exactly once. For failed payments I wire up dunning, retries, and clear status in your database. I also build reconciliation checks so your records and the provider's records always agree, even after outages or replays.

Q.Do you work remotely with clients in other time zones?

Yes. I work solo and remote with global clients. I keep communication clear with async updates, a shared scope document, and short calls when we need them. You get direct access to the engineer doing the work, no account manager in between. I overlap working hours where it helps and document everything for handover.

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Start your project

Tell me what you are building and I will reply within one business day with next steps. You talk to me, the person writing the code, the whole way through.