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API Development Services in the USA
PerfectionGeeks builds custom APIs for US businesses: REST and GraphQL APIs for web and mobile apps, third-party integrations with Salesforce, Stripe, Epic, Shopify and more, public developer APIs with portals and SDKs, and modernisation of legacy SOAP and on-premise systems. Every API ships with OpenAPI documentation, authentication, rate limiting, automated tests and monitoring, and is designed for SOC 2, HIPAA, PCI DSS or CCPA requirements where they apply. A single integration typically costs $8,000–$25,000; a custom application API $25,000–$75,000; and an API platform $75,000–$200,000+.
12+Years Building Software
200+Projects Delivered
4.9/5Clutch Rating (45+ Reviews)
- Start API projects with an API-first design: an OpenAPI or GraphQL schema agreed before coding saves rework.
- Choose the style by use case: REST for most apps and partners, GraphQL for complex front ends, gRPC for internal services, webhooks and events for real-time updates.
- Security is the biggest risk: follow the OWASP API Security Top 10, with strong authentication, authorisation checks, rate limits and logging.
- US compliance shapes design: HIPAA for health data, PCI DSS for card data, SOC 2 for SaaS buyers and state privacy laws such as CCPA.
- Typical cost: $8K–$25K per integration, $25K–$75K for a custom API, $75K–$200K+ for API platforms.
What Is API Development?
What Is API Development?
Our API Development Services in the USA
Custom API Development
REST and GraphQL APIs that power your web apps, mobile apps and internal tools.
Third-Party API Integration
Connect Salesforce, HubSpot, Stripe, QuickBooks, NetSuite, Shopify, Twilio, Epic and other platforms.
Public and Partner API Development
Developer-facing APIs with API keys or OAuth, usage plans, a developer portal, SDKs and sandbox environments.
Microservices and Event-Driven APIs
Internal service APIs, gRPC, message queues and webhooks for real-time, scalable systems.
Legacy API Modernisation
Wrap or replace SOAP, XML and on-premise interfaces with modern REST or GraphQL APIs, without breaking existing clients.
API Security and Testing
OWASP API Security Top 10 reviews, penetration testing, contract tests and load tests.
API Gateway and Management
Set up AWS API Gateway, Azure API Management, Apigee or Kong for authentication, throttling, analytics and versioning.
AI and LLM APIs
Build APIs that serve AI features, connect to Claude, GPT or Gemini, and expose tools for AI agents through standards such as the Model Context Protocol.
API Monitoring and Support
Uptime and latency monitoring, error tracking, version management and ongoing improvements.
Types of APIs We Build
| API style | Best for | Strengths | Trade-offs |
|---|---|---|---|
| REST | Most web and mobile apps, partner integrations | Simple, widely understood, easy to cache | Can need several calls for complex screens |
| GraphQL | Complex front ends and mobile apps with varied data needs | Clients fetch exactly what they need in one request | Caching and query cost control need care |
| gRPC | High-performance internal microservices | Fast binary protocol, strong contracts | Less suited to browsers and public APIs |
| Webhooks | Notifying partners of events such as payments or orders | Real-time, simple for consumers | Need retries, signing and idempotency |
| Event streaming (Kafka, SNS/SQS) | High-volume, decoupled systems | Scales well, resilient | More infrastructure to run |
| SOAP (legacy) | Older enterprise and government systems | Formal contracts, mature tooling | Verbose, harder for modern clients |
API Use Cases by US Industry
| Industry | Common API projects | Compliance to plan for |
|---|---|---|
| Healthcare | EHR integration with Epic or Oracle Health via FHIR, telehealth, patient apps, RPM device data | HIPAA, BAAs, ONC interoperability rules |
| Fintech and banking | Payments, account aggregation with Plaid, card issuing, KYC, ledgers | PCI DSS, GLBA, SOC 2, state money transmission rules |
| Retail and eCommerce | Shopify, BigCommerce, Amazon and marketplace integrations, inventory and order sync | PCI DSS, CCPA and state privacy laws |
| Logistics | Carrier APIs (UPS, FedEx, USPS), tracking, warehouse and TMS integrations | Customer data protection |
| SaaS | Public APIs, webhooks, SSO and integrations marketplaces | SOC 2, enterprise security reviews |
| Insurance | Quoting, policy and claims APIs, partner portals | State insurance data rules, GLBA |
| Real estate | MLS feeds, CRM and transaction management integrations | MLS licensing rules, privacy laws |
Features of a Well-Built API
Clear contract
OpenAPI 3 or GraphQL schema, consistent naming and predictable errors.
Authentication and authorisation
OAuth 2.0 and OpenID Connect, API keys for server-to-server use, scoped permissions.
Rate limiting and quotas
Protection from abuse and fair use for every client.
Versioning
A plan for changes that does not break existing clients.
Pagination, filtering and idempotency
Safe retries and efficient large data sets.
Observability
Logs, metrics, tracing and alerts.
Documentation and SDKs
Interactive docs, examples and client libraries.
Performance
Caching, efficient queries and response times that meet agreed targets.
API Security: How We Protect Your APIs
We also add input validation, secrets management, audit logs, dependency scanning and independent penetration tests before launch.
| OWASP API risk | What we do |
|---|---|
| Broken object-level authorisation | Check on every request that the caller may access that specific record |
| Broken authentication | OAuth 2.0 and OIDC, short-lived tokens, MFA for admin access, secure key storage |
| Broken property-level authorisation | Return only allowed fields; block mass assignment |
| Unrestricted resource use | Rate limits, quotas, payload size limits and timeouts |
| Broken function-level authorisation | Role-based access for admin and sensitive endpoints |
| Server-side request forgery | Validate and restrict outbound URLs |
| Security misconfiguration | Hardened gateways, TLS 1.2+, CORS rules, security headers |
| Improper inventory | Catalogue every API and version; retire old ones |
| Unsafe consumption of third-party APIs | Validate data from partners and set timeouts and fallbacks |
US Compliance We Design For
HIPAA
Encryption, access controls, audit logs and BAAs for APIs that handle protected health information.
PCI DSS v4.0
Tokenisation and certified payment providers so card data stays out of your systems where possible.
SOC 2
Controls and evidence (access reviews, change management, monitoring) that help SaaS companies pass customer security reviews.
GLBA
Safeguards for consumer financial information.
CCPA/CPRA and other state privacy laws
Data minimisation, access and deletion requests and consent records.
ONC interoperability rules
Standard FHIR APIs for certified health IT and patient access.
API Development Technology Stack
| Layer | Technologies |
|---|---|
| Languages and frameworks | Node.js (NestJS, Express), Python (FastAPI, Django REST), Java (Spring Boot), Go, .NET |
| API styles | REST with OpenAPI 3, GraphQL (Apollo), gRPC, webhooks |
| Gateways | AWS API Gateway, Azure API Management, Google Apigee, Kong |
| Messaging | Kafka, RabbitMQ, AWS SNS and SQS, EventBridge |
| Databases | PostgreSQL, MySQL, MongoDB, DynamoDB, Redis |
| Identity | Auth0, Okta, Amazon Cognito, Azure AD B2C, Keycloak |
| Testing | Postman, Newman, Pact contract tests, k6 or JMeter load tests |
| Documentation | Swagger UI, Redoc, Stoplight, developer portals |
| Observability | Datadog, New Relic, Grafana, OpenTelemetry, Sentry |
| Cloud | AWS, Azure, Google Cloud with US regions |
How Much Does API Development Cost in the USA?
What drives cost: number of endpoints and integrations, data complexity, security and compliance needs, performance targets, documentation and SDKs, and the state of legacy systems. Ongoing costs include hosting, gateway and monitoring fees and maintenance, typically 15–20% of the build cost a year.
| Scope | What is included | Cost (USD) | Timeline |
|---|---|---|---|
| Single third-party integration | One platform (for example Stripe, Salesforce or Shopify), mapping, error handling, tests | $8,000–$25,000 | 2–5 weeks |
| Custom application API | REST or GraphQL API for a web or mobile app, authentication, database, docs, tests | $25,000–$75,000 | 6–12 weeks |
| Integration platform or middleware | Several systems connected with queues, retries, monitoring and dashboards | $50,000–$150,000 | 3–6 months |
| Public API platform | Developer portal, API keys and OAuth, usage plans, SDKs, sandbox, analytics | $75,000–$200,000+ | 4–8 months |
| Legacy API modernisation | New API layer over legacy systems, migration and parallel running | $50,000–$250,000+ | 3–9 months |
Engagement Models and US Time-Zone Delivery
Our US office is in Laguna Beach, California, and our engineering teams arrange daily overlap with US Pacific and Eastern business hours for stand-ups, reviews and urgent support.
| Model | How it works | Best for |
|---|---|---|
| Fixed price | Agreed scope, price and timeline | Defined integrations and MVP APIs |
| Time and materials | Pay for hours used with flexible scope | Evolving products and modernisation |
| Dedicated API team | A monthly team of engineers, QA and a lead | Long-term API programmes |
Our API Development Process
API design (API-first)
Write the OpenAPI or GraphQL schema, resources, errors and versioning approach, and review it with your team before coding.
Architecture
Choose frameworks, gateway, authentication, database, caching and messaging; plan environments and CI/CD.
Development
Build endpoints in sprints with code reviews, unit tests and mock servers so front-end teams can start early.
Testing
Functional, contract, security (OWASP), performance and load tests, plus integration tests with partner sandboxes.
Documentation
Interactive docs, examples, Postman collections and SDKs where needed.
Deployment
Automated deployment to staging and production with monitoring, alerts and rollback plans.
Support and evolution
Monitoring, version management, new endpoints and performance tuning.
API Development Best Practices We Follow
API Development Best Practices We Follow
Common API Challenges and How We Solve Them
| Challenge | How we solve it |
|---|---|
| Breaking changes for existing clients | Versioning, deprecation notices and contract tests |
| Slow responses under load | Caching, query optimisation, async processing and autoscaling |
| Unreliable third-party APIs | Timeouts, retries with backoff, circuit breakers and queues |
| Security incidents | OWASP API Top 10 controls, gateway policies and monitoring |
| Poor developer adoption | Clear docs, quick-start guides, SDKs and a sandbox |
| Legacy system limits | An API layer that hides legacy complexity and migrates in phases |
Why Choose PerfectionGeeks for API Development in the USA
API-first engineering
OpenAPI and GraphQL contracts, documentation and tests in every project.
Integration depth
Salesforce, Stripe, Plaid, Epic and FHIR, Shopify, NetSuite, Twilio and more.
US compliance awareness
HIPAA, PCI DSS, SOC 2 and state privacy laws built into design.
US time-zone collaboration
A US office and daily overlap with Pacific and Eastern hours.
Cost-effective delivery
Onshore leadership with offshore engineering for strong value.
You own it
Source code, documentation and API specifications belong to you.
Proven delivery
12+ years, 200+ projects and a 4.9/5 rating on Clutch from 45+ reviews.
Related Reading
Related Reading
Build Your Secure API With Our Experts
Tell us what your API needs to do, which systems it must connect to and any compliance requirements. Within 2 business days we will send an API design approach, timeline and cost estimate, under an NDA.
Client Testimonials
Frequently Asked Questions
How much does API development cost in the USA?
A single third-party integration typically costs $8,000–$25,000, a custom application API $25,000–$75,000, an integration platform $50,000–$150,000 and a public API platform $75,000–$200,000 or more.
How long does it take to build an API?
About 2–5 weeks for a single integration, 6–12 weeks for a custom application API and 3–8 months for integration or public API platforms.
What is the difference between REST and GraphQL?
REST exposes fixed endpoints for resources and is simple and widely supported. GraphQL uses one endpoint where clients ask for exactly the fields they need, which suits complex front ends but needs more care with caching and query costs.
How do you secure APIs?
We follow the OWASP API Security Top 10 with OAuth 2.0 and OIDC, object-level authorisation checks, rate limits, input validation, encryption, audit logs, monitoring and penetration testing.
Can you build HIPAA-compliant APIs?
Yes. We build healthcare APIs with encryption, access controls, audit logs and FHIR integration, host them on HIPAA-eligible cloud services and sign a BAA.
Can you build PCI DSS-compliant payment APIs?
Yes. We use tokenisation and certified providers such as Stripe or Adyen so raw card data stays out of your systems, reducing PCI scope.
Can your APIs integrate with third-party services?
Yes. We integrate CRMs, ERPs, payment providers, EHRs, eCommerce platforms, shipping carriers, messaging services and AI models.
Do you provide API documentation?
Yes. Every API includes OpenAPI or GraphQL schemas, interactive documentation and examples, and we can build developer portals and SDKs.
Can you modernise our legacy SOAP or on-premise APIs?
Yes. We add a modern REST or GraphQL layer, migrate clients in phases and retire old interfaces safely.
Do you work in US time zones?
Yes. We have a US office in Laguna Beach, California, and our teams overlap daily with US Pacific and Eastern business hours.
Who owns the API code?
You do. Source code, specifications and documentation are assigned to you under the contract.
Do you provide support after launch?
Yes. We provide monitoring, bug fixes, version management, performance tuning and new endpoints under monthly support plans.