REST (Representational State Transfer)

The architectural standard that powers every digital interaction — from mobile banking to e-commerce checkout to AI-powered chatbots.

REST APIs carry an estimated 80-90% of all internet application traffic, making them the backbone of modern digital business. Every time a customer checks their bank balance on a mobile app, places an order on an e-commerce site, or asks a voice assistant for the weather, a REST API is working behind the scenes. The global API management market — built primarily around REST — exceeded $8 billion in 2025 and is projected to reach $20 billion by 2030. For C-suite leaders, REST is not a technical detail but the lingua franca of digital business: it is how your systems, partners, and customers communicate.

What It Is

REST (Representational State Transfer) is an architectural style for designing networked applications, first described by computer scientist Roy Fielding in 2000. In practice, REST defines a set of conventions for building APIs — the interfaces through which different software systems communicate over the internet. A RESTful API uses standard HTTP methods (GET to retrieve data, POST to create data, PUT to update data, DELETE to remove data) and organises data into resources identified by URLs. When you visit "api.company.com/customers/12345," you are making a REST request to retrieve data about customer number 12345.

Think of a REST API as a well-organised filing cabinet with a standardised request form. Every file (resource) has a unique location (URL). You use the same simple form (HTTP methods) to interact with any file: "Retrieve the file for customer 12345" (GET), "Create a new file for this customer" (POST), "Update the address on customer 12345's file" (PUT), or "Remove customer 12345's file" (DELETE). The filing cabinet sends back responses in a standard format (typically JSON — a lightweight, human-readable data format) that any system can understand. This standardisation is what makes REST so powerful: any application written in any programming language can interact with any REST API, using the same simple conventions.

REST's simplicity and universality are its greatest strengths. Unlike earlier approaches such as SOAP (which required complex XML messaging and specialised tooling), REST leverages the same HTTP protocol that powers the World Wide Web. Every developer already knows HTTP, every programming language has HTTP libraries, and every network infrastructure (firewalls, load balancers, proxies) is designed to handle HTTP traffic. This means REST APIs can be built, tested, and deployed quickly, and they work reliably across any network environment.

Why It Matters for Business

REST APIs are the foundation of platform business models and digital ecosystems. When Stripe makes its payment processing available via REST APIs, any company in the world can integrate payment capabilities in hours rather than months. When Twilio offers communication APIs, startups can build SMS and voice capabilities without negotiating carrier contracts. Salesforce's REST API ecosystem generates over $5 billion in annual partner revenue, with thousands of companies building products that integrate with the Salesforce platform. The ability to expose your business capabilities as REST APIs — creating what is often called an "API-first" strategy — enables new revenue streams, partner integrations, and customer experiences that would be impossible with closed, proprietary systems.

Internally, REST APIs enable the modern enterprise technology stack. Your CRM talks to your marketing automation via REST APIs, which talks to your analytics platform via REST APIs, which talks to your data warehouse via REST APIs. This API-mediated architecture allows individual systems to be upgraded or replaced without disrupting the entire ecosystem — a critical capability when the average enterprise replaces 15-20% of its SaaS tools annually. Companies that invest in well-designed internal REST APIs report 25-40% faster development of new integrations and features.

REST also plays a central role in the emerging API economy, where business capabilities are consumed as services. Companies like Amazon, Google, and Microsoft operate vast API platforms that process trillions of requests per month. Amazon's e-commerce API alone processes over 1 billion requests per day during peak periods, enabling millions of third-party sellers to list products, process orders, and manage inventory programmatically. The API economy is projected to represent 10% of global GDP by 2030, with REST as its primary technical enabler.

Enterprise Use Cases

Amazon built its entire empire on APIs. In the early 2000s, CEO Jeff Bezos issued his famous "API Mandate" requiring every team to expose their data and functionality through APIs (specifically RESTful interfaces). This mandate enabled Amazon Web Services — initially built by exposing Amazon's internal infrastructure capabilities as REST APIs. Today, AWS processes trillions of API requests per month across over 200 services, generating over $100 billion in annual revenue. The same API-first approach enabled Amazon Marketplace, which allows millions of third-party sellers to operate on Amazon's platform, now accounting for over 60% of Amazon's total unit sales.

Starbucks built its mobile ordering system — which processes over 30% of all US store orders — on REST APIs connecting the mobile app to point-of-sale systems, inventory management, and loyalty programme databases. During peak morning hours, the system handles over 5,000 orders per minute via REST endpoints that complete in under 200 milliseconds. In healthcare, Epic Systems' FHIR (Fast Healthcare Interoperability Resources) API standard is built on REST, enabling electronic health record systems to share patient data across hospitals and providers. The 21st Century Cures Act mandates that healthcare providers make patient data available via standardised REST APIs, giving patients direct access to their health information through third-party applications.

Spotify's entire platform is built on a REST API architecture that serves over 600 million users. The public API enables over 100,000 developers to build integrations, from DJ apps that sync with Spotify playlists to smart home systems that play music on command. Internally, over 1,500 microservices communicate via REST APIs, enabling the company to deploy hundreds of updates daily.

Vendor Landscape

REST itself is an architectural standard, not a product — there are no "REST vendors" in the traditional sense. However, the ecosystem of tools for building, managing, and securing REST APIs is substantial. API management platforms — Apigee (Google, with enterprise pricing from $500 per month to six-figure annual contracts), Kong (open-source and enterprise, from $35,000 per year), AWS API Gateway ($3.50 per million requests plus data transfer), and Azure API Management ($49-349 per month per unit) — provide traffic management, security, rate limiting, and analytics for REST APIs. API documentation tools include Swagger/OpenAPI (the industry standard specification, now managed by the Linux Foundation) and Postman (used by over 30 million developers, with enterprise plans from $12 per user per month). For testing REST APIs, tools include Postman, Insomnia, and automated testing frameworks like REST Assured. For designing and mocking APIs before development begins, Stoplight and SwaggerHub provide collaborative design environments.

Strategic Considerations

Adopt an API-first strategy: design your REST APIs before building the systems that implement them. This ensures that APIs are designed from the consumer's perspective (what does the client need?) rather than the provider's convenience (what is easiest to implement?). Invest in comprehensive API documentation — the single most important factor in API adoption, whether for internal developers or external partners. Implement robust API governance including versioning strategy (how you evolve APIs without breaking existing consumers), rate limiting (preventing any single consumer from overwhelming your systems), and authentication/authorisation (typically OAuth 2.0). Consider the balance between REST and emerging alternatives: GraphQL for flexible data querying, gRPC for high-performance internal service communication, and WebSockets for real-time bidirectional communication. Each has strengths, and most enterprise architectures use a combination. For external partner and public APIs, REST remains the default choice due to its universal understanding and tooling support.