Custom API Integration Services — Stripe, OpenAI, Twilio & Third-Party APIs

From $150

Seamlessly connect your application to third-party APIs — Stripe payments, OpenAI / AI models, Twilio SMS, Mapbox, and more. Webhook handling, error resilience, rate limiting, and full TypeScript type safety.

What's Included

Stripe Payments
Subscriptions & Webhooks
Net Banking
OpenAI Chat
Embeddings & Structured Outputs
AI Streaming Responses (SSE)
RAG / Vector Search (pgvector / Pinecone)
Twilio SMS
OTP & Voice
Mapbox / Google Maps Integration
Webhook Signature Verification
Idempotent Webhook Processing
BullMQ Async Job Queues
TypeScript-Typed Service Layer
Retry Logic & Circuit Breakers
React Email Templates (Resend / SendGrid)
AWS S3 / Cloudflare R2 File Uploads
Full API Error Handling & Logging
Razor Pay (UPI Wallet)

Custom API Integration — Connect Everything. Break Nothing.

Modern web applications are built on integrations. Your users expect Stripe-quality payment flows, instant SMS notifications, AI-powered features, and real-time map experiences — all without leaving your product. But connecting third-party APIs isn't just fetch(url, { headers: { Authorization: apiKey } }). Done right, API integration means robust error handling, webhook signature verification, retry logic, rate limit management, and a clean abstraction layer that makes your codebase maintainable as APIs evolve. Done wrong, it means silent failures, security vulnerabilities, and integration code scattered everywhere.

API Integrations I Specialize In

Stripe — Payments, Subscriptions & Billing

Stripe is the most feature-rich payment platform available — and also the most complex to implement correctly. I've integrated Stripe across dozens of projects and know exactly where the edge cases hide.

What I implement:

Stripe Checkout — hosted payment page for one-time purchases with configurable line items
Stripe Elements — custom-styled embedded payment form matching your design exactly
Payment Intents API — 3D Secure / SCA-compliant payment flows for European customers
Subscriptions — recurring billing with free trials, upgrade/downgrade, and proration
Usage-based billing — metered billing for APIs, AI tokens, or compute-based pricing
Stripe Connect — marketplace and platform payments with connected accounts and automatic payouts
Stripe Webhooks — full webhook handler for all relevant events, with signature verification and idempotency
Stripe Customer Portal — self-service subscription and payment method management
Razorpay — India-specific payment gateway with UPI, net banking, and wallet support

OpenAI & AI Model Integrations

AI features are now a baseline expectation for modern software. I integrate OpenAI's APIs — and alternatives like Anthropic Claude, Google Gemini, and open-source models via Ollama or HuggingFace — into production applications with streaming, caching, and cost management built in.

Integrations I build:

Chat completions — conversational AI assistants with streaming responses (text/event-stream) and conversation history management
Structured outputs — JSON mode and function calling for extracting structured data from unstructured text (e.g., parsing resumes, extracting entities)
Embeddings + vector search — storing text embeddings in pgvector or Pinecone for semantic search and RAG (Retrieval-Augmented Generation) applications
Image generation — DALL-E 3 integration for user-triggered image generation with content policy handling
Whisper — audio transcription for voice input features and meeting note tools
Fine-tuned model deployment — calling custom fine-tuned models via the OpenAI fine-tuning API
Token usage tracking — per-user token consumption logging for usage-based billing

Production considerations I handle:

Response streaming for instant perceived performance
Prompt injection prevention and input sanitization
Cost controls — max token limits, per-user rate limits, and spend alerts via OpenAI usage APIs
Fallback logic — automatic retry on 429 Too Many Requests, fallback to a secondary model on 503
System prompt management — environment-stored, version-controlled prompts

Twilio — SMS, Voice & Verification

SMS notifications — transactional SMS for order confirmations, appointment reminders, and alerts via Twilio Messaging
OTP / phone verification — Twilio Verify for phone number verification flows (6-digit code via SMS or voice call)
Programmable voice — outbound call initiation and inbound call handling via TwiML
WhatsApp Business API — customer support and notification messaging via Twilio's WhatsApp integration
Two-way SMS — webhook receiver for inbound messages, enabling SMS-based support flows

Mapbox & Google Maps

Mapbox GL JS — custom-styled interactive maps with markers, popups, clustering, and route drawing
Geocoding API — converting addresses to coordinates and vice versa for location-based features
Directions API — turn-by-turn routing for delivery tracking, service area visualization
Mapbox Tilesets — custom data overlays (heatmaps, choropleth maps) from your own datasets
Google Maps Places API — autocomplete address inputs, place details, and nearby search
Geofencing — location-based triggers for field service apps and delivery tracking

Email APIs

Resend — transactional email via React Email templates, with open and click tracking
SendGrid — bulk transactional and marketing email with template management
React Email — building email templates as React components with preview server
Nodemailer — SMTP-based email for self-hosted or enterprise mail server setups
Email webhook handling — bounce, complaint, unsubscribe, and delivery event processing

Other Integrations

Service	Use Case
Google Calendar / Outlook	Booking and scheduling systems
Slack / Discord	Internal notifications and webhooks
GitHub API	Developer tools, CI dashboards
Notion API	Content management and knowledge bases
Airtable API	No-code database backends
Shopify Storefront API	Headless e-commerce frontends
HubSpot / Salesforce CRM	Lead capture and CRM sync
Cloudinary	Image upload, transformation, and CDN
AWS S3 / Cloudflare R2	File storage and presigned URL uploads
Plaid	Bank account connection and transaction data
Lemon Squeezy	Digital product sales and licensing

How I Build Integrations

Service Layer Pattern

Every API integration is wrapped in a typed service module — not scattered across route handlers:

/lib
  /stripe
    stripe.ts          — client initialization
    checkout.ts        — checkout session creation
    webhooks.ts        — webhook handler + event router
    subscriptions.ts   — subscription management
  /openai
    client.ts
    chat.ts
    embeddings.ts
  /twilio
    sms.ts
    verify.ts

This means the integration logic is testable in isolation, the API client is initialized once, and route handlers stay clean.

Webhook Handling

Webhooks are where most integrations fail in production. I implement:

Signature verification on every webhook — Stripe's stripe.webhooks.constructEvent(), Twilio's X-Twilio-Signature, GitHub's X-Hub-Signature-256
Idempotency — webhook events stored with their IDs; duplicate deliveries are no-ops, not double-processed charges
Async processing — webhook endpoints acknowledge immediately (return 200) and hand off to a BullMQ queue for processing, preventing timeout failures
Dead letter queues — failed webhook processing retried with exponential backoff, then moved to a dead letter queue for manual inspection

Error Handling & Resilience

Typed error classes per integration — StripeError, OpenAIError, TwilioError with structured error data
Retry logic — exponential backoff on retryable errors (rate limits, temporary service unavailability)
Circuit breaker pattern — failing fast when a third-party service is down, rather than queuing up thousands of hanging requests
Fallback behavior — graceful degradation when non-critical integrations fail (e.g., analytics event fails silently; payment flow never does)
Logging — every API call logged with request parameters, response status, and latency for debugging

Technology Stack

TypeScript · Stripe SDK · OpenAI SDK · Twilio SDK · Mapbox GL JS · React Email + Resend · BullMQ · Zod · Axios · Next.js Route Handlers · Prisma · Redis (Upstash)

Ready to start?

Let's discuss how we can help with your project.

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