REST Fundamentals

This article is a definition of terms for REST – including exam questions, practical example, and tags.

In a Nutshell

REST is an architectural style for distributed HTTP-based systems: resources are addressed via URIs, manipulated through methods, and transferred via representations. Goal: loose coupling, scalability, caching.

Compact Technical Description

REST defines six constraints:

• Client-Server
• Statelessness
• Cache-ability
• Uniform Interface
• Layered
• Optional Code on Demand

Resources are business objects (e.g., /orders/42). Representations transport state (JSON/XML), negotiated via Accept/Content-Type.

Method semantics:

• GET: safe + idempotent
• POST: not idempotent
• PUT: idempotent
• PATCH: not necessarily idempotent
• DELETE: idempotent

Status codes signal successes/failures (200/201/204/400/401/403/404/409/500). HATEOAS uses links in representations for “discoverable” workflows. Caching uses Cache-Control, ETag, If-None-Match.

Exam-Relevant Key Points

• Resource-oriented URI design (no verbs in path)
• Safe/Idempotent semantics of methods
• Status codes correct (Location for 201)
• Idempotency Key for POST (if needed)
• Security: TLS, OAuth/OIDC/JWT, CORS, Rate Limiting
• Cost-effectiveness: loose coupling
• Documentation: OpenAPI + error catalog

Core Components

1. Resource + URI Design
2. Representations + Media Types
3. Method Semantics
4. Status Codes + Headers
5. Content Negotiation
6. Caching (ETag)
7. Security
8. Versioning
9. Observability
10. Tests (Contract/API)

Practical Example (Orders + HATEOAS)

{
  "id": 42,
  "status": "created",
  "links": [
    { "rel": "self", "href": "/orders/42" },
    { "rel": "confirm", "method": "POST", "href": "/orders/42/confirm" }
  ]
}

Advantages and Disadvantages

Advantages

• Interoperability through standards
• Loose coupling
• Good scalability through statelessness
• Efficient caching

Disadvantages

• Overfetching/Underfetching possible
• Complex write processes require idempotency strategies
• HATEOAS is often not applied consistently

Typical Exam Questions (with Brief Answers)

1. What REST constraints exist? Client-Server, Stateless, Cache, Uniform Interface, Layered, optional Code on Demand.
2. PUT vs PATCH regarding idempotency? PUT idempotent, PATCH not automatically.
3. How do ETag + conditional requests work? Client sends If-None-Match, server responds with 304 or delivers new body.

Free Response

REST is more than “JSON over HTTP”: the constraints and method semantics are decisive. Clean error objects, versioning, and observability make APIs maintainable.

Learning Strategy

1. Analyze public APIs and assign constraints.
2. Design resource model (URIs/methods/status codes).
3. Practice method semantics table (safe/idempotent).
4. Avoid verbs in path.

Most Important Sources

1. https://roy.gbiv.com/untangled
2. https://www.rfc-editor.org/rfc/rfc9110
3. https://learn.microsoft.com/azure/architecture/best-practices/api-design