In today’s interconnected software landscape, choosing the right API architecture can make or break your application’s success. Four fundamental API architectures – REST, GraphQL, Webhooks, WebSockets – each offers unique strengths, and understanding when to use each one is crucial for building modern and scalable applications.

The most common question developers face is: “Which API architecture should I use?”. The truth is, there’s no single “best” choice. Each architecture solves different problems, and the most successful projects often use multiple approaches together. Let’s dive into when and why you should choose each one.

REST: The Reliable Foundation

REST (Representational State Transfer) remains the foundation of modern APIs, with approximately 70% of public APIs using this architecture. Its popularity stems from simplicity, reliability and broad ecosystem support.

REST excels at standard CRUD (Create, Read, Update, Delete) operations. It’s stateless by design, making it easy to scale horizontally. The architecture uses standard HTTP methods (GET, POST, PUT, DELETE) and resource-based URLs, which makes it intuitive for developers to understand and implement.

For OpenEdge developers, REST is the natural starting point. PASOE (Progress Application Server for OpenEdge) provides native REST support, allowing you to expose your business logic as REST APIs without significant code changes.

Here’s a simple example:

/* CustomerService.cls - PASOE REST Service */

@openapi.openedge.export(type="GET").
METHOD PUBLIC VOID GetCustomer(INPUT id AS INTEGER, OUTPUT TABLE ttCustomer):
 DEFINE BUFFER bCustomer FOR Customer.

 FIND FIRST bCustomer
  WHERE bCustomer.CustNum = id
  NO-LOCK NO-ERROR.

 IF AVAILABLE bCustomer THEN DO:
  CREATE ttCustomer.
  BUFFER-COPY bCustomer TO ttCustomer.
 END.
END METHOD. 

Use REST when you need: public APIs for third parties, standard CRUD operations, microservices communication, or simple mobile app backends. Its main challenges include over-fetching or under-fetching data, requiring multiple round trips for related data and API versioning complexity.

GraphQL: The Query Revolution

GraphQL, developed by Facebook in 2012, solves REST’s data fetching problems by letting the client specify exactly what data it needs. Instead of fixed endpoints returning predetermined data structures, GraphQL provides a single endpoint where clients can query for precisely the fields they want.
Consider this scenario: with REST, fetching a user with their posts and comments requires three separate requests. With GraphQL, you express it in a single query:

query {
 user(id: 123) {
  name
  email
  posts {
   id
   total
   comments { author }
  }
 }
}

This flexibility makes GraphQL exceptional for complex user interfaces and mobile applications where bandwidth efficiency matters. The strongly typed schema provides excellent developer experience and self-documenting APIs.

However, OpenEdge doesn’t have native GraphQL support. The practical solution is the gateway pattern: keep your business logic in OpenEdge exposed via REST APIs, then add a Node.js GraphQL server (using Apollo Server, for example) that aggregates and transforms those REST endpoints. This approach gives your frontend the modern API experience while keeping your proven OpenEdge business logic unchanged.

Use GraphQL when you have: React/Vue/Angular apps with complex data requirements, mobile apps needing bandwidth efficiency, multiple client applications with different data needs or when you want to aggregate multiple data sources. The tradeoffs include more complex backend setup, harder caching, query complexity management challenges and a steeper learning curve for teams.

Webhooks: Event-Driven Efficiency
 

Webhooks solve a fundamental problem: how do you know when something happens in another system without constantly checking? Traditional polling wastes bandwidth and introduces latency. Webhooks flip the model – when an event occurs, the server immediately notifies your application via an HTTP POST request.

Think of webhooks as “reverse APIs”. Instead of you calling an API repeatedly asking “Has anything changed?”, the service calls your endpoint saying “Here’s what changed.”
Common use cases include payment confirmations from Stripe, shipping notifications from logistics providers, form submissions, Git push notifications from GitHub and CRM updates from Salesforce.

For OpenEdge integration, webhooks work in two directions:

Receiving webhooks (external service → your application):

/* WebhookHandler.cls */

METHOD PUBLIC VOID HandleStripeWebhook(
 INPUT cPayload AS LONGCHAR,
 INPUT cSignature AS CHARACTER):

 /* 1. Verify signature */
 IF NOT ValidateSignature(cPayload, cSignature)
 THEN RETURN ERROR "Invalid signature".

 /* 2. Parse JSON */
 ASSIGN oJson = NEW JsonObject().
 oJson:Read(cPayload).

 /* 3. Update order */
 RUN UpdateOrderStatus(
  oJson:GetInteger("orderId"),
  "paid"
 ).
END METHOD. 

Sending webhooks (your application → external service):

/* SendWebhook.p */

METHOD PRIVATE VOID SendWebhook():
 DEFINE VARIABLE hClient AS HANDLE NO-UNDO.
 DEFINE VARIABLE cPayload AS LONGCHAR NO-UNDO.

 /* Build JSON payload */
 cPayload = SUBSTITUTE(
  '~{"event": "order.shipped",' +
  '"orderId": &1,' +
  '"trackingNumber": "&2"~}',
  iOrderId, cTrackingNum
 ).

 /* Send HTTP POST */
 CREATE "System.Net.WebClient" hClient.
 hClient:Headers:Add("Content-Type", "application/json").
 hClient:Headers:Add("X-Webhook-Signature", GenerateSignature(cPayload)).

 cResponse = hClient:UploadString(
  "https://crm.com/webhooks/orders",
  "POST",
  cPayload
 ).

 DELETE OBJECT hClient.
END METHOD. 

Critical webhook best practices: always verify webhook signatures to prevent malicious requests, respond within 3 seconds to avoid timeouts, implement retry logic for failed deliveries and ensure your webhook endpoint is publicly accessible.

Use webhooks for payment processing integrations, shipping and logistics updates, form submissions, IoT sensor alerts or any event-driven workflow where immediate notification matters.

WebSockets: Real-Time Bi-Directional Power

WebSockets provide true bi-directional, real-time communication between client and server. Unlike REST’s request-response cycle or webhooks’ one-way notifications, WebSockets maintain a persistent connection where both client and server can push data at any time.

The key difference from traditional HTTP: instead of opening a new connection for each request, WebSockets establish one connection that stays open, enabling ultra-low latency (1-10ms) communication.

WebSockets vs Webhooks confusion: despite similar names, these are fundamentally different. Webhooks are one-time HTTP requests (connect -> send -> disconnect) for event notifications. WebSockets are persistent bi-directional connections for continuous real-time data flow.

Like GraphQL, OpenEdge doesn’t have native WebSocket support. The solution is again the gateway pattern: a Node.js WebSocket server (using Socket.io) maintains connections with browsers, polls your OpenEdge REST API for updates (every 1-5 seconds) and pushes changes to connected clients instantly.

Use WebSockets for live chat applications, collaborative editing tools (like Google Docs), real-time dashboards, gaming, stock tickers or any scenario requiring instant two-way communication.

The Decision Framework: Choosing the Right Tool

Here’s your quick reference guide:

Simple mobile app, standard    ————————————->    CRUD REST
Complex UI, flexible data fetching    ——————————>    GraphQL
React to external events (async)    ———————————>    Webhooks
Live updates, two-way communication    ———————–>    WebSockets
Integrating with OpenEdge    —————————————>    REST (primary)
Public API for third parties    ——————————————>    REST
Real-time collaborative features    ———————————>    WebSockets
Payment notifications from Stripe    ——————————>    Webhooks

The most important insight: modern applications rarely use just one architecture. A typical e-commerce platform might use:

– REST for product catalog, user authentication, order management,
– GraphQL for mobile app data fetching and personalized recommendations,
– Webhooks for payment confirmations, shipping updates, inventory changes,
– WebSockets for live inventory updates, customer support chat, real-time order tracking.

OpenEdge Modernization Strategy

For OpenEdge developers, here’s the recommended phased approach:

Phase 1: Expose REST endpoints via PASOE (your foundation).
Phase 2: Add GraphQL gateway for flexible queries (if needed).
Phase 3: Implement WebSocket layer for real-time features (if needed).
Phase 4: Integrate webhooks for event-driven workflows.

The core principle: keep your business logic in OpenEdge where it belongs. Add modern API layers on top. There’s no need to rewrite everything – your proven business logic remains stable and reliable while you gain modern API capabilities.

Conclusion

There’s no universal “best” API architecture—only the right one for your specific use case. REST provides your reliable foundation. GraphQL offers flexible queries for complex UIs. Webhooks enable efficient event-driven integrations. WebSockets power real-time bi-directional features.

For OpenEdge developers, start with REST as your primary interface. As your application grows and requirements evolve, strategically add GraphQL, WebSocket and webhook layers to solve specific problems. The most successful modern applications use all four architectures together, each playing to its strengths.

Remember: choose per use case, not per project. Each architecture excels at different problems, and understanding when to apply each one will dramatically improve your application’s architecture, performance and developer experience.

Author: Carla Spaczai, Developer

Curious and driven, Carla grew from intern to full-time developer through dedication and a genuine love of learning. She’s passionate about making technology more intuitive and human, and when she’s not coding, she’s usually exploring a new idea or skill to master.