API Development & Integration
Connect disparate systems with modern, secure APIs — REST, GraphQL, gRPC. Integrate AI models, payment platforms, and enterprise systems.
Modern APIs That Connect Your Business
We design, build, and maintain APIs that enable seamless data flow between your systems.
In today's enterprise landscape, the ability to connect systems, share data, and automate workflows across organizational boundaries is not a luxury — it is a competitive necessity. HEXCLOUD.AI provides end-to-end API development and integration services that transform fragmented technology ecosystems into unified, data-driven platforms. Whether you need to connect your ERP system with your CRM, integrate AI capabilities powered by OpenAI, Gemini, or self-hosted models, implement payment processing with Stripe, or build a real-time event-driven architecture that reacts to business events in milliseconds — our team has the expertise to deliver robust, secure, and well-documented APIs that stand the test of time and scale.
Our approach to API development starts with design, not code. We work with your business analysts and technical stakeholders to map data flows, identify integration requirements, and define API contracts using OpenAPI 3.1 specifications before writing a single endpoint. This design-first methodology ensures that APIs are consistent, well-documented, and aligned with business needs. On the implementation side, we leverage .NET 8 for high-performance RESTful services, Node.js for lightweight event-driven APIs, GraphQL for flexible data-fetching scenarios, and gRPC for low-latency inter-service communication. We also integrate large language models (LLMs) from OpenAI, Google Gemini, and local deployments via Ollama — building production-grade AI pipelines with prompt management, token optimization, and provider fallback chains. Every API is secured with OAuth 2.0, rate-limited to prevent abuse, and monitored with real-time dashboards that track latency, error rates, and usage patterns across all consumers.
For payment and billing workflows, we have successfully delivered Stripe integrations for SaaS products — from one-time payments to complex subscription models with metered billing, proration, and dunning. Our open-source Stripe reference implementation demonstrates our approach to clean, production-ready payment integration. We also build custom integrations for any third-party service — if it has an API, we can connect it.
What makes HEXCLOUD.AI different is our focus on the full integration lifecycle. We do not just build APIs and walk away — we implement comprehensive monitoring, maintain SDKs for your consumers, manage versioning and deprecation, and provide SLA-backed support. Our integration projects consistently deliver measurable outcomes: one recent client reduced data synchronization errors by 94% after we replaced their file-based integration with a real-time API-driven architecture. Another client cut their average order processing time from 45 minutes to under 3 minutes by connecting their eCommerce platform directly to their warehouse management system through our API middleware. These are the kinds of results that justify the investment in modern integration infrastructure.
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Integration Expertise
Ten core capabilities covering API design, security, enterprise connectors, AI/LLM integration, payment processing, and operational excellence.
API Design (REST / GraphQL / gRPC)
We design APIs that developers love to use. For public-facing services, we build RESTful APIs following the OpenAPI 3.1 specification with comprehensive Swagger documentation. For complex data-fetching scenarios, we implement GraphQL with schema stitching and federation. For high-performance inter-service communication, we use gRPC with Protocol Buffers. Every API design goes through a review process that evaluates consistency, versioning strategy, error handling, and pagination patterns before a single line of code is written.
Authentication & Security (OAuth 2.0 / JWT)
Secure every API endpoint with industry-standard authentication and authorization mechanisms. We implement OAuth 2.0 authorization flows (client credentials, authorization code with PKCE), JWT token validation, API key management with rate limiting, and mutual TLS for service-to-service communication. All APIs include input validation, SQL injection prevention, CORS configuration, and request/response logging for audit trails.
Enterprise Integrations (SAP, Salesforce, Dynamics)
Connect your enterprise systems with custom integrations that handle the complexity of SAP RFC/BAPI calls, Salesforce REST and Bulk APIs, Microsoft Dynamics 365 Web API, and other enterprise platforms. We build robust integration layers with retry logic, dead-letter queues, data transformation pipelines, and comprehensive error handling. Our connectors handle millions of records daily with guaranteed delivery and data consistency.
Microservices & Event-Driven Architecture
Design and implement event-driven architectures using Azure Service Bus, RabbitMQ, or Apache Kafka. Each microservice communicates asynchronously through well-defined events, enabling loose coupling and independent scalability. We implement the saga pattern for distributed transactions, event sourcing for audit-critical domains, and the outbox pattern to guarantee message delivery even when databases and message brokers are temporarily inconsistent.
SDK Generation & Developer Portal
Accelerate third-party adoption of your APIs with auto-generated SDKs for C#, JavaScript/TypeScript, Python, and Java. We set up developer portals with interactive API documentation (Swagger UI or Redoc), sandbox environments for testing, usage examples, and getting-started guides. SDKs are versioned, published to package registries (NuGet, npm), and maintained alongside your API releases.
Monitoring, SLA & Rate Limiting
Full API observability with request/response logging, latency tracking, error rate monitoring, and custom dashboards. We implement rate limiting policies per client, per endpoint, and per time window to protect your infrastructure from abuse. SLA monitoring tracks uptime, response times, and error budgets with automated alerting when thresholds are breached. Historical analytics help you understand API usage patterns and plan capacity.
API Gateway & Traffic Management
Deploy and configure API gateways (Azure API Management, Kong, or AWS API Gateway) that handle cross-cutting concerns: authentication, rate limiting, request transformation, response caching, and load balancing. We implement routing policies, version management through URL paths or headers, request/response transformation, and backend circuit breakers. Gateway configuration is managed as code and deployed through CI/CD pipelines.
Webhook Management & Event Delivery
Build reliable webhook delivery systems that notify external systems in real-time when events occur in your application. Our webhook infrastructure includes signature verification (HMAC-SHA256), exponential backoff retry logic, delivery status tracking, failed delivery alerting, and a management UI for subscribers to register endpoints and view delivery logs. We guarantee at-least-once delivery with idempotency support on the consumer side.
AI & LLM Integration (OpenAI, Gemini, Ollama)
Integrate large language models into your business workflows with production-grade API wrappers. We connect your applications to cloud providers like OpenAI (GPT-4o, o1), Google Gemini, and Anthropic Claude, as well as self-hosted models running on Ollama for full data sovereignty. Our AI integration layer handles prompt management, token optimization, streaming responses, fallback chains between providers, structured output parsing, and usage tracking. Whether you need intelligent document processing, conversational interfaces, code generation pipelines, or custom-trained models served via API, we build the integration infrastructure that makes AI reliable and cost-effective at scale.
Payment & Billing Integration (Stripe)
Implement robust payment processing with Stripe and other payment platforms. We build complete billing workflows including one-time payments, recurring subscriptions with metered billing, invoicing, refunds, and webhook-driven lifecycle management. Our Stripe integrations handle SCA/3D Secure compliance, multi-currency support, tax calculation, proration, dunning for failed payments, and PCI-DSS compliant checkout flows. We have successfully delivered Stripe payment systems for SaaS products and marketplaces — see our open-source reference implementation on GitHub.
Integration Architecture
A hub-and-spoke topology connecting your enterprise systems through a central API gateway.
How We Deliver
Eight structured phases from discovery and architecture design through testing, go-live, and ongoing evolution.
Discovery & Analysis
We audit your existing systems, data flows, third-party services, and integration points. We document current API contracts, identify data inconsistencies, map business processes, and define the target integration architecture. For AI integrations, we evaluate model requirements, data sensitivity, and hosting preferences (cloud vs. on-premise). Deliverables include a system inventory, data flow diagrams, risk assessment, and a comprehensive integration requirements document.
Architecture & Design
Our architects design the API contracts using OpenAPI 3.1 specification, define data schemas, establish naming conventions, and design error handling patterns. For AI-powered endpoints, we design prompt templates, define fallback strategies, and establish model selection criteria. For payment integrations, we design the billing lifecycle, webhook flows, and reconciliation logic. All designs go through stakeholder review before development begins.
Development & Integration
API development follows test-driven practices with contract tests written first. We implement API logic, data validation, business rules, and database queries. AI integrations include prompt engineering, streaming response handlers, and token optimization. Payment integrations include Stripe Connect setup, subscription lifecycle, and webhook consumers. Every endpoint includes comprehensive input validation, proper HTTP status codes, and descriptive error messages.
Security Audit
Dedicated security review including OWASP API Security Top 10 assessment, authentication flow verification, authorization testing, rate limiting validation, input fuzzing, and penetration testing. For AI endpoints, we test for prompt injection, data leakage, and output validation. For payment flows, we verify PCI-DSS compliance, SCA/3D Secure implementation, and webhook signature validation. Deliverable: a security assessment report with remediation evidence.
Testing & QA
Comprehensive testing across multiple layers: unit tests for business logic, integration tests for API contracts, end-to-end tests for critical workflows, load tests to validate throughput under peak conditions, and chaos engineering tests to verify resilience. AI integrations undergo evaluation against benchmark datasets to measure accuracy, latency, and cost. Payment integrations are tested in Stripe sandbox with all edge cases: failed payments, subscription upgrades/downgrades, refunds, and disputes.
Go-Live & Migration
Staged rollout with traffic shifting from legacy integrations to new APIs. We implement feature flags for gradual migration, monitor error rates and latency during cutover, and maintain rollback capability. Post-launch hypercare includes 24/7 monitoring for the first two weeks with immediate incident response. Data migration is handled with zero-downtime strategies and validation checksums.
SDK & Documentation
Auto-generate client SDKs from OpenAPI specifications, publish to package registries, set up the developer portal with interactive documentation, and create migration guides. AI integration documentation includes prompt library, model configuration, and usage guidelines. Payment documentation covers billing API, webhook event catalog, and testing guides.
Ongoing Support & Evolution
Post-delivery support includes proactive monitoring, performance optimization, and iterative improvements based on usage analytics. We manage API versioning, deprecation cycles, and consumer migration. AI model updates, prompt refinements, and cost optimization are handled as part of continuous improvement. Monthly reports track API health, usage trends, error rates, and optimization opportunities.
Our Integration Tech Stack
Proven tools and frameworks for building reliable, scalable API infrastructure.
ERP-CRM-eCommerce Integration Hub
Challenge
A mid-size manufacturing company had critical business data trapped in silos across SAP Business One (ERP), Salesforce (CRM), and a Magento eCommerce platform. Order data was manually re-entered between systems, causing delays, errors, and inconsistent customer information. Staff spent an estimated 120 hours per month on manual data synchronization tasks.
Solution
We built a central API integration hub using .NET 8 with Azure Service Bus for asynchronous messaging. Custom connectors were developed for each system: SAP DI API for ERP, Salesforce REST API for CRM, and Magento REST API for eCommerce. The hub implements data transformation, conflict resolution, and guaranteed message delivery with comprehensive audit logging. A monitoring dashboard provides real-time visibility into all integration flows.
Results
Frequently Asked Questions
Common questions about our API development and integration services.
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Let's Design Your Integration Architecture.
Start with a free API strategy session. We'll map your systems, identify quick wins, and propose an integration roadmap tailored to your business needs.