API Development Services in the USA
Senior API Development Company Building REST, GraphQL & gRPC APIs
Your systems should talk to each other. As a senior API development company, we design, build, and integrate secure, scalable REST, GraphQL, and gRPC APIs, plus third-party integrations across payments, CRM, ERP, and AI, all under one senior backend engineering team in the USA.
Triple API Guarantee
- 99.9% Uptime SLA
- OAuth2 / JWT Secured
- OpenAPI Documented
Triple API Guarantee:
- 99.9% Uptime SLA
- OAuth2 / JWT Secured
- OpenAPI Documented
APIs Built
0
+
Uptime SLA
0
%
Integrations
0
+
API Service Suite
REST APIs
200+ Built
GraphQL APIs
80+ Built
gRPC Services
40+ Built
Integrations
50+ Platforms
Webhooks
Real-Time
API Gateways
Kong / AWS
Auth & Security
OAuth2 / JWT
Microservices
Event-Driven
API Docs
OpenAPI
API Calls / Month
50M+
On-Time Delivery
96%
↑ 4%
Repeat Clients
81%
Trusted By Startups
The Value of One Trusted API Development Company in the USA
Stallyons is a senior API development company serving founders, product leaders, and enterprise teams across 50+ industries in the USA. We are not a freelancer marketplace or a generalist agency. We are a full backend engineering team that designs, builds, secures, documents, and scales the APIs your business runs on.
Most teams bolt an API onto an app as an afterthought and get three different definitions of "done." We have watched it for fifteen years: undocumented endpoints, brittle integrations, no versioning strategy, and auth that leaks. The result is a fragile layer that breaks every time traffic spikes or a partner changes their payload. We build APIs the opposite way, contract-first and production-grade from the first commit.
Our Full API Development Range
REST API Development: Resource-based, cacheable, versioned REST APIs on Node.js, Python (FastAPI/Django), .NET, and Java/Spring, engineered for speed, security, and scale from the first endpoint.
GraphQL API Development: Strongly-typed schemas, resolvers, and federation with Apollo and Relay, so clients fetch exactly the data they need in a single request, ideal for mobile and complex data graphs.
gRPC & Real-Time APIs: Low-latency, Protobuf-based service-to-service communication over HTTP/2, plus WebSockets and webhooks for event-driven, real-time systems.
Third-Party Integrations: Payments (Stripe, PayPal, Braintree, Adyen), CRM and ERP (Salesforce, HubSpot, NetSuite, SAP), and AI providers (OpenAI, Anthropic Claude, Gemini), wired in cleanly with retries, idempotency, and reconciliation.
API Gateways, Auth & Security: Kong, Apigee, AWS API Gateway, and Azure APIM with OAuth2, JWT, OIDC, rate limiting, throttling, and key management, aligned to SOC 2, HIPAA, and PCI-DSS.
API-First Architecture & Microservices: Event-driven microservices, message queues (Kafka, RabbitMQ, SNS/SQS), and OpenAPI/Swagger documentation, so your platform stays modular and scalable as it grows.
Why Stallyons Is the API Development Company Businesses Trust
- Contract-First, Not Afterthought: We design the OpenAPI or GraphQL schema before writing code, so front-end, mobile, and partner teams build in parallel against a stable contract. No breaking changes, no guesswork.
- Senior Backend Engineers Only: No outsourced juniors. The engineer who designs your API architecture ships the code and reviews the PRs. Security, idempotency, and versioning decisions are made by people who have run APIs at scale.
- Secure by Design: OAuth2/JWT auth, role-based access control, TLS, input validation, rate limiting, and secret management on every endpoint, aligned to SOC 2, HIPAA, GDPR, and PCI-DSS from day one, not bolted on after a pen test fails.
- Documented & Testable: Every API ships with OpenAPI/Swagger specs, an interactive portal, Postman collections, SDKs, and contract tests, so your team and partners integrate in hours, not weeks.
- Built to Scale: Caching, connection pooling, pagination, async processing, and horizontal scaling designed in from the start. When call volume multiplies, your API holds instead of timing out.
- You Own Everything: Clean, documented code, infrastructure-as-code, and no black boxes. 81% of clients come back for their next engagement because the APIs keep working long after launch.
How to Start Your API Project
Every engagement starts with a free 45-minute API architecture session, no slide deck and no sales script. You bring the goal (a new API, an integration, a versioning strategy, or a performance fix) and leave with a clear scope, a recommended protocol, and a realistic timeline.
We are selective about new engagements and cap our active client count to keep the senior-engineer-to-project ratio high. If we take your API on, it gets a senior backend team, not a queue and a junior.
Why Clients Choose Us
200+
APIs Built & Deployed
50+
Third-Party Integrations
81%
Repeat Client Rate
4.9/5
Clutch Rating
Ready to connect your systems with secure, scalable APIs built by one senior backend team?
API Capabilities
Every API Capability Your Product Needs Under One Roof
From protocol design to third-party integrations, gateways, and documentation. Pick one capability, or let us assemble the full API layer.
REST APIs
Resource-based, cacheable, versioned endpoints
HTTP / JSON
GraphQL APIs
Typed schemas, resolvers, federation
APOLLO / RELAY
gRPC & Protobuf
Low-latency, service-to-service
HTTP/2
Payment Integrations
Stripe, PayPal, Braintree, Adyen
4 GATEWAYS
CRM & ERP Sync
Salesforce, HubSpot, NetSuite, SAP
4 SYSTEMS
API Gateways
Kong, Apigee, AWS, Azure APIM
4 GATEWAYS
Auth & Identity
OAuth2, JWT, OIDC, Auth0, Okta
5 METHODS
Webhooks & Events
Kafka, RabbitMQ, SNS/SQS, webhooks
4 TECHNOLOGIES
AI & LLM APIs
OpenAI, Claude, Gemini wiring
1 SUITE
API Docs & Portals
OpenAPI, Swagger, Postman, SDKs
4 CAPABILITIES
Not sure which API capabilities fit your roadmap? Let's map it together.
Common Challenges
Are Disconnected Systems Holding Your Business Back?
These integration pain points quietly cost you hours, revenue, and growth, and most stay invisible until an API breaks in production.
Disconnected Systems & Data Silos
01
Your CRM, ERP, storefront, and app each hold a different version of the truth. Without a clean API layer, teams re-key data by hand and reports never reconcile.
Manual Work & Human Error
02
Orders copied between tools, invoices re-typed, leads exported and imported. Every manual hop is a place for errors to creep in and hours to leak away.
Fragile, Undocumented APIs
03
A previous team shipped endpoints with no OpenAPI spec, no versioning, and no tests. Every integration is reverse-engineering, and every change risks breaking a partner.
APIs That Break Under Load
04
Traffic doubles and the API starts timing out. No caching, no pagination, no rate limiting. What worked in the demo collapses the day it matters most.
Security & Compliance Gaps
05
Weak auth, keys in code, no rate limiting, and endpoints that leak data. One audit or one breach turns a shortcut into a very expensive problem.
Vendor Lock-In & Rate Limits
06
A third-party integration throttles you, changes its payload, or hikes its price, and your whole workflow stalls because nothing was built to swap it out cleanly.
Recognize any of these? Let's fix your API layer.
Our API Services
6 API Development Services Built to Compound
Each service is a senior backend team. Mix, match, or run them in parallel. Every layer is built to make the others faster, safer, and easier to scale.
REST API Development
01
Resource-based, cacheable, versioned REST APIs on Node.js, Python (FastAPI/Django), .NET, and Java/Spring. Clean routes, proper status codes, pagination, and idempotency, engineered for speed and scale.
GraphQL API Development
02
Strongly-typed schemas, efficient resolvers, and Apollo federation so clients request exactly the data they need in one round trip. Ideal for mobile apps and complex, related data graphs.
gRPC & Real-Time APIs
03
Low-latency, Protobuf-based gRPC services over HTTP/2 for service-to-service calls, plus WebSockets and webhooks for event-driven, real-time features that need to push updates instantly.
Third-Party Integrations
04
Payments (Stripe, PayPal, Braintree, Adyen), CRM and ERP (Salesforce, HubSpot, NetSuite, SAP), and AI providers (OpenAI, Claude, Gemini), wired with retries, idempotency, and reconciliation so nothing double-charges or drops.
API Security & Gateways
05
OAuth2, JWT, and OIDC auth, role-based access control, rate limiting, and throttling behind Kong, Apigee, AWS API Gateway, or Azure APIM. SOC 2, HIPAA, and PCI-DSS-aligned from day one.
Microservices & API-First Architecture
06
Event-driven microservices, message queues (Kafka, RabbitMQ, SNS/SQS), API versioning strategy, and OpenAPI/Swagger documentation, so your platform stays modular, observable, and easy to scale.
Need to combine several of these into one API engagement?
Why Partner with Us?
The Business Results You Get With Our API Development Services
What you get when design, engineering, security, and documentation are owned by one senior backend team.
Systems That Finally Talk
01
One clean API layer connects your CRM, ERP, storefront, and app. Data flows automatically, reports reconcile, and your team stops re-keying by hand.
2-3x Faster Integration
02
Senior engineers who have wired hundreds of integrations skip the discovery loops and ship in weeks, with contract-first design that lets your other teams build in parallel.
Secure by Design
03
OAuth2/JWT, rate limiting, encryption, and access control on every endpoint. SOC 2, HIPAA, GDPR, and PCI-DSS-aligned engineering, audit-ready on day one.
Fully Documented
04
OpenAPI/Swagger specs, an interactive portal, Postman collections, and SDKs ship with every API, so your team and partners integrate in hours, not weeks.
Built to Scale
05
Caching, pagination, async processing, and horizontal scaling designed in from the start. When call volume multiplies, your API holds instead of timing out.
81% Come Back
06
Most clients return for their next engagement, because the APIs keep working long after launch, and you own every line of code.
Ready for an API layer that delivers real business results?
Our Process
From Architecture to Live API in 6 Proven Steps
A structured, transparent process built to deliver secure, scalable, well-documented APIs your business can rely on.
Discovery
API architecture & requirements mapping
Design
Contract-first OpenAPI / GraphQL schema
Build
Agile sprints, versioned endpoints
Integrate
Payments, CRM, ERP, AI, webhooks
Secure & Test
Auth, load, security, contract tests
Deploy & Scale
Gateway, monitoring, versioning, support
Want to see how this maps to your specific API project?
Technology Stack
The Full API Development Stack We Build On
Modern, battle-tested tools across every layer of an API, protocols, gateways, data stores, messaging, and cloud.
Web & Backend
Next.js / React
Node.js / Vue
Python / Django
.NET / Java
TypeScript
Mobile & Cross-Platform
Swift / iOS
Kotlin / Android
React Native
Flutter
Ionic / HarmonyOS
AI / ML / Data
OpenAI / Claude
Gemini / Qwen
PyTorch / TensorFlow
Hugging Face
SageMaker / Vertex AI
Ecommerce & CMS
Shopify / Plus
BigCommerce
WooCommerce
Magento / OpenCart
Webflow / Framer
Cloud & DevOps
AWS / GCP / Azure
Docker / K8s
Terraform / IaC
GitHub Actions / CI
Datadog / Grafana
Technology Stack
The Full API Development Stack We Build On
Modern, battle-tested tools across every layer of an API, protocols, gateways, data stores, messaging, and cloud.
Web & Backend
Next.js / React
Node.js / Vue
Python / Django
.NET / Java
TypeScript
Mobile & Cross-Platform
Swift / iOS
Kotlin / Android
React Native
Flutter
Ionic / HarmonyOS
AI / ML / Data
OpenAI / Claude
Gemini / Qwen
PyTorch / TensorFlow
Hugging Face
SageMaker / Vertex AI
Ecommerce & CMS
Shopify / Plus
BigCommerce
WooCommerce
Magento / OpenCart
Webflow / Framer
Cloud & DevOps
AWS / GCP / Azure
Docker / K8s
Terraform / IaC
GitHub Actions / CI
Datadog / Grafana
Industries We Serve
APIs for 50+ Industries, From Startups to the Fortune 500
API and integration expertise across the industries where connected systems compound revenue, speed, and competitive moat.
Fintech & Banking
Payments, KYC, regulatory tech
Healthcare & HealthTech
HIPAA, telehealth, clinical SaaS
Retail & E-Commerce
DTC, B2B, marketplace, headless
EdTech & Learning
LMS, course platforms, proctoring
Manufacturing & Industrial
IoT, predictive maintenance, MES
Logistics & Supply Chain
Routing, fleet, warehouse, B2B
Legal & LegalTech
Document AI, contract analysis
Media & Entertainment
Streaming, content AI, audience
We know your vertical's systems and compliance rules. Let's connect them with APIs built to last.
How We Compare
API Development Company vs Freelancers vs In-House
An honest look at your API development and integration options.
| Capability | Freelancer | In-House Team | Cheap Agency | Stallyons Technologies |
|---|---|---|---|---|
| REST, GraphQL & gRPC Expertise | ✕ One Protocol | Depends | Junior Team | Senior + All Three |
| Contract-First Design (OpenAPI) | ✕ Rarely | Sometimes | ✕ Skipped | Every Build |
| OAuth2 / JWT Security & Compliance | ✕ Basic | Varies | Add-On Fee | SOC 2 / HIPAA |
| Full API Documentation & Portal | ✕ None | Internal Only | Extra $ | Included |
| Rate Limiting & Gateways | ✕ DIY | Sometimes | Inconsistent | Kong / APIM |
| Third-Party Integrations | Limited | Slow | Fragile | Payments / CRM / AI |
| 99.9% Uptime & Scalability | ✕ No SLA | Varies | ✕ Best-Effort | SLA-Backed |
| You Own the Code | Maybe | Yes | Partial | 100% Yours |
See the difference for yourself
Complete Engagement
Everything You Get With Our API Development Partnership
From Architecture to Launch to Scale All Under One Roof
Here's everything included when you build your API with Stallyons:
All-Inclusive API Development: No Vendor Sprawl, No Hidden Fees.
Every engagement includes all 8 components above. REST, GraphQL, gRPC, integrations, security, and docs, delivered by one senior backend team. One contract, one quality bar.
🔒 No obligation. We'll deliver a detailed proposal within 48 hours.
Plus, Get These Free Bonuses
Free API Architecture Audit
A 30-point review of your current APIs and integrations, covering security, documentation, versioning, performance, and scaling gaps. Yours free whether you hire us or not.
Included Free
API Roadmap & Estimate
A phased delivery plan with endpoint map, protocol recommendation, integration dependencies, milestones, and a transparent, itemized estimate for your project.
Included Free
Proof-of-Concept Sprint
For qualifying engagements, a 1-week PoC sprint at no cost, building a working endpoint or integration so you see senior backend work product before committing.
Included Free
Risk-Free Partnership
Our API Development Guarantee
We stand behind every API we build with measurable commitments that protect your investment.
01
99.9% Uptime SLA
We commit to a 99.9% uptime SLA with monitoring, alerting, and horizontal scaling built in. If your API misses the mark after launch, we fix it at no extra cost.
02
Secure & Compliant
OAuth2/JWT auth, rate limiting, encryption, and access control on every endpoint, with SOC 2, HIPAA, GDPR, and PCI-DSS-aligned engineering and documentation ready for auditor review.
03
60-Day Bug-Free Guarantee
Senior engineers, code-review gates, contract tests, and load and security testing on every project. For 60 days after launch, any bug we introduced we fix free.
Build your API with zero risk, backed by our Triple API Guarantee.
Track Record
Engagements That Ship, Scale, and Compound
500+
Projects Delivered
29+
Service Categories
81%
Repeat Client Rate
4.9 ★
Clutch Rating
"We came to Stallyons after burning two years and four vendors on a multi-platform launch that kept slipping. They scoped it end-to-end — web app, iOS, Android, an AI summarization layer, and a Shopify integration — and shipped it in 22 weeks. One team, one budget, one quality bar. We've handed them three more engagements since."
Mark Sawyer
CEO/Founder
PlatinumLED
"Stallyons rebuilt our customer-facing portal, integrated three legacy systems, shipped an AI document analysis pipeline, and brought our compliance posture to SOC 2 — all under one engagement. The senior engineers on the team have shipped at companies five times our size. It's the best vendor decision we've made in a decade."
Mark Sawyer
CEO/Founder
PlatinumLED
FAQ
Frequently Asked Questions About API Development
An API (Application Programming Interface) is a contract that lets different software systems talk to each other. Your business needs APIs to automate workflows, integrate third-party services like payments and CRM, power mobile apps, share data securely with partners, and eliminate manual re-keying between systems.
Simple REST APIs with basic CRUD operations typically take 2-4 weeks. More complex APIs with multiple integrations, GraphQL or gRPC, advanced authentication, and full documentation usually take 6-12 weeks. We give you a detailed timeline during the free architecture session.
REST uses fixed endpoints returning predefined structures, great for simple, cacheable operations. GraphQL lets clients request exactly the data they need in one call, ideal for mobile and complex data graphs. gRPC uses Protobuf over HTTP/2 for very low-latency service-to-service communication. We help you pick the right protocol, or combine them, for each use case.
We layer multiple controls: OAuth2 or JWT authentication, role-based access control, HTTPS/TLS encryption, input validation, rate limiting, throttling, and API-key management. For regulated industries we align to SOC 2, HIPAA, and PCI-DSS, and every API ships with security tests.
Projects typically start around $15,000, including architecture design, development, security, documentation, and 90 days of support. Complex enterprise integrations with many endpoints and third-party systems generally range from $25,000 to $75,000. You get a transparent, itemized estimate before any work begins.
Yes, complete documentation is included with every project. You receive OpenAPI/Swagger specifications, an interactive documentation portal, code samples in multiple languages, Postman collections, SDKs, and a testing environment, so your team and external developers integrate easily.
Every project includes 90 days of post-deployment support covering bug fixes, minor adjustments, and monitoring. We also offer ongoing maintenance plans with 24/7 monitoring, security patches, version updates, and dedicated support. Your API is never abandoned after launch.
Absolutely. We connect your APIs to payments (Stripe, PayPal, Braintree, Adyen), CRM and ERP (Salesforce, HubSpot, NetSuite, SAP), messaging, and AI providers (OpenAI, Claude, Gemini), with retries, idempotency, and reconciliation so data stays consistent and nothing double-processes.
Still have questions? Let's talk.
Schedule an appointment with us today!
Ready to Connect Your Business to Everything?
Get a free 45-minute API architecture session. Bring the systems you need connected, walk away with a clear integration path, protocol recommendation, and a proposal within 48 hours.
