AWS API Error: REST API vs HTTP API — Why the Same Request Behaves Differently
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How to understand and debug differences in routing, authorization, error responses, and request handling between API Gateway REST APIs and HTTP APIs when identical requests produce different results
Problem
You send the same HTTP request to two APIs in Amazon API Gateway—one built as a REST API, the other as an HTTP API—and observe different behavior.
Examples include:
- One API returns
403 Forbidden, the other returns401 - One API returns
Missing Authentication Token, the other returns404 - One API invokes the backend, the other never reaches it
- One API requires explicit configuration, the other “just works”
From the client’s perspective, this looks inconsistent. From API Gateway’s perspective, it is expected.
Clarifying the Issue
Although they share a name and a console, REST APIs and HTTP APIs are fundamentally different products with different design goals.
They differ in:
- How routes are matched
- How authorization is enforced
- How errors are surfaced
- How much configuration is required versus implied
The mistake is assuming:
❌ “HTTP APIs are just a cheaper, faster version of REST APIs.”
They are not. They are different execution models, and that difference becomes most visible during debugging.
Why It Matters
Many teams:
- Migrate from REST APIs to HTTP APIs for cost or latency
- Mix REST and HTTP APIs within the same account
- Debug issues using the wrong mental model
When you apply REST API expectations to an HTTP API, you will:
- Misinterpret error codes
- Look for configuration that does not exist
- Miss defaults that are silently applied
Correctly identifying the API type up front prevents unnecessary rework.
Key Terms
- REST API – Feature-rich API Gateway offering with explicit configuration
- HTTP API – Streamlined API Gateway offering with opinionated defaults
- Route – A path + method combination
- Integration – The backend target (Lambda, HTTP endpoint, etc.)
- Authorizer – Logic that determines whether a request is allowed
- Stage – A deployment snapshot (REST) or logical environment (HTTP)
Steps at a Glance
- Identify which API type you are using
- Understand how routing differs
- Understand how authorization differs
- Compare common error behaviors
- Adjust debugging approach accordingly
Detailed Steps
Step 1: Identify the API Type
In the API Gateway console:
- REST APIs are labeled explicitly as REST
- HTTP APIs are labeled explicitly as HTTP
Do not begin debugging until this is confirmed.
Step 2: Understand Routing Differences
REST APIs
- Routes are defined via Resources + Methods
- Routing is strict and explicit
A missing method or path commonly results in:
Missing Authentication Token
HTTP APIs
- Routes are defined as method + path patterns
- Routing is simpler and more permissive
A missing route typically results in:
404 Not Found
Key distinction:
✅ REST APIs obscure route existence
✅ HTTP APIs surface standard HTTP semantics
Step 3: Understand Authorization Differences
REST APIs
Support multiple authorization mechanisms:
- IAM authorization
- Lambda authorizers (IAM policy–based responses)
- Cognito authorizers
- Resource policies
Authorization is deeply configurable and tightly coupled to methods.
HTTP APIs
Support a smaller, opinionated set:
- IAM authorization
- Lambda authorizers (simplified response contract)
- JWT authorizers (OIDC / Cognito)
While HTTP APIs do support Lambda Authorizers, the contract is different:
- REST API authorizers return IAM policy documents
- HTTP API Lambda authorizers return simple authorization responses, such as:
{ "isAuthorized": true }
REST API authorizer code cannot be reused verbatim with HTTP APIs without modification. This difference frequently causes confusion during migrations.
Step 4: Error Behavior Differences
The same underlying problem can produce different errors:
| Scenario | REST API | HTTP API |
|---|---|---|
| Route does not exist | Missing Authentication Token | 404 Not Found |
| Authorization fails | 403 Forbidden | 401 or 403 |
| Method not allowed | Missing Authentication Token | 404 |
| Deployment missing | Missing Authentication Token | Not applicable (with Auto-Deploy) |
These differences are intentional.
Step 5: Deployment Model Differences
REST APIs
- Require explicit deployment to a stage
- Changes do not take effect until deployed
- Undeployed changes commonly surface as routing errors
HTTP APIs
- Auto-Deploy is enabled by default
- Changes typically apply immediately
- Manual deployments and stages are still supported when Auto-Deploy is disabled
This default behavior removes an entire class of deployment-related errors, but can surprise teams expecting REST-style workflows.
Pro Tips
- Always confirm the API type before debugging.
- Do not assume error codes map 1:1 across API types.
- REST APIs favor control; HTTP APIs favor simplicity.
- “Missing Authentication Token” is largely a REST API concern.
- HTTP APIs trade flexibility for predictability.
Conclusion
REST APIs and HTTP APIs in API Gateway may look similar, but they behave differently by design.
When the same request produces different results:
- REST APIs reflect explicit configuration and obscure routing failures
- HTTP APIs apply defaults and surface clearer HTTP semantics
Once your mental model aligns with the API type in use, debugging becomes deterministic instead of frustrating. The behavior stops being surprising—and starts being informative.
Aaron Rose is a software engineer and technology writer at tech-reader.blog and the author of Think Like a Genius.
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