AWS API Gateway Error: Stage Drift & Deployment Confusion
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How API Gateway changes appear correct in the console but fail at runtime due to undeployed updates, stage-specific configuration, canary deployments, or drift between stages
Problem
You update an API in Amazon API Gateway—add a route, change authorization, modify an integration—and everything looks correct in the console.
But when you invoke the API:
- The old behavior is still active
- Requests fail with routing or authorization errors
- A change that “should work” does nothing
Common symptoms include:
Missing Authentication Token403 Forbidden- Unexpected integration behavior
- One stage working while another does not
- Intermittent behavior that defies logic
The configuration looks right.
The runtime behavior disagrees.
Clarifying the Issue
API Gateway does not execute the configuration you see in the editor.
It executes a deployed snapshot of that configuration—per stage.
This creates a class of problems known as stage drift, where:
- The API definition is updated
- But the stage is not redeployed
- Or the wrong stage is being invoked
- Or a canary deployment is partially overriding behavior
- Or stages have diverged over time
In short:
đź“Ś You changed the API, but not the runtime artifact actually serving traffic.
Why It Matters
Stage drift is one of the most time-consuming API Gateway failures because:
- The console UI implies changes are “live”
- Multiple stages share a single API definition
Each stage can have unique:
- Variables
- Logging
- Throttling
- Authorizers
- Canary settings
Errors look identical to routing or authorization failures
Teams often respond by:
- Editing IAM policies
- Rewriting integrations
- Rolling back code
None of which fix an undeployed, mis-targeted, or partially overridden stage.
Key Terms
- Stage – A deployed snapshot of an API configuration
- Deployment – Publishing API changes to a stage
- Deployment History – Timestamped record of deployments to a stage
- Stage Drift – Divergence between edited configuration and runtime behavior
- Canary Deployment – Partial traffic routing to a newer deployment
- Invoke URL – The stage-specific endpoint used by clients
Steps at a Glance
- Confirm which stage the client is calling
- Verify deployment using Deployment History
- Understand which changes require redeployment
- Check for stage-specific drift (variables, auth, logging)
- Ensure no stale Canary Deployment is active
- Redeploy intentionally and retest
Detailed Steps
Step 1: Confirm the Target Stage
Inspect the Invoke URL used by the client:
https://abc123.execute-api.us-east-1.amazonaws.com/dev/resource
The stage (dev, prod, etc.) is part of the path.
Common mistakes:
- Modifying
prodwhile callingdev - Testing via an old bookmark
- Calling a custom domain mapped to a different stage
If you’re calling the wrong stage, no configuration change will help.
Step 2: Verify Deployment via Deployment History (Source of Truth)
Do not rely on memory or assumptions.
In the API Gateway console:
- Open the Stage
- Navigate to Deployment History
- Check the Created Date timestamp
If the deployment timestamp is older than your last edit, then your change is not deployed, regardless of what the editor shows.
This timestamp is the only reliable proof of what is running.
Step 3: Know Which APIs Are Affected
This problem primarily affects:
- REST APIs
- HTTP APIs with Auto-Deploy disabled
For HTTP APIs, Auto-Deploy is enabled by default, which avoids most stage drift issues.
If you are working with a REST API (or manually deployed HTTP API), deployment is always explicit.
Step 4: Check Stage-Specific Configuration Drift
Even with a fresh deployment, stages may behave differently.
Each stage can independently configure:
- Stage variables
- Logging and metrics
- Throttling limits
- Authorizer associations
- Cache behavior
A fix applied at the API level may still fail if the stage configuration diverged earlier.
Step 5: Check for Active Canary Deployments (Critical Check)
This is a subtle but dangerous source of drift.
If a Canary Deployment is enabled:
- Only a percentage of traffic uses the new deployment
- The rest continues to hit the old one
If the canary is never promoted:
- You get split-brain behavior
- Tests appear inconsistent
- Fixes seem to “sometimes work”
Before debugging further, verify:
- No stale canary is active
- Or the canary has been fully promoted
Step 6: Redeploy Intentionally and Retest
Once you have confirmed:
- Correct stage
- Deployment timestamp is current
- Stage configuration is aligned
- No canary is overriding behavior
Redeploy deliberately and retest.
A clean redeploy often resolves the issue immediately—without touching IAM, code, or integrations.
Pro Tips
- Deployment History beats intuition.
- Stages are the runtime; the editor is not.
- Canaries cause intermittent, maddening behavior.
- Different stages are allowed to behave differently—by design.
- Redeploying is safe; guessing is expensive.
Conclusion
Most API Gateway “mystery failures” attributed to routing or authorization are actually stage execution problems.
When behavior doesn’t match expectation:
- Check the stage
- Check the deployment timestamp
- Check for canaries
- Check for drift
Once configuration and runtime are aligned, many problems disappear instantly.
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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