5 Serverless Pitfalls That Almost Tanked Our Production System (And How We Fixed Them)
Lessons from scaling to 2M+ requests/day on AWS Lambda
#serverless #aws #devops #architecture #cloud
1. Cold Starts: The Silent Performance Killer
❌ Our mistake: Ignored latency spikes during sporadic traffic.
✅ Fix:
bash
`
Enable Provisioned Concurrency for critical Lambdas
aws lambda put-provisioned-concurrency-config \
--function-name OrderProcessor \
--qualifier LIVE \
--provisioned-concurrent-executions 50
`
Result: P99 latency dropped from 4200ms → 210ms.
2. Permission Overload in IAM Roles
❌ Our mistake: Used "Resource": "*" for DynamoDB access.
✅ Fix:
json
`
// Least-privilege policy
{
"Effect": "Allow",
"Action": [
"dynamodb:PutItem",
"dynamodb:Query"
],
"Resource": "arn:aws:dynamodb:us-east-1:1234567890:table/Orders"
}
`
Result: Reduced breach risk surface by 83%.
3. Observability Blind Spots
❌ Our mistake: Relied solely on CloudWatch.
✅ Fix: Implemented structured logging with AWS X-Ray:
javascript
`const AWSXRay = require('aws-xray-sdk-core');
AWSXRay.captureAWS(require('aws-sdk'));
// Annotate traces
const segment = AWSXRay.getSegment();
segment.addAnnotation('CheckoutFlow', 'started'); `
Result: Debug time reduced from hours → minutes.
4. Unbounded Concurrency Costs
❌ Our mistake: No limits on Lambda scaling.
✅ Fix: Set account-wide concurrency limits:
terraform
`
resource "aws_lambda_function" "processor" {
function_name = "payment-worker"
reserved_concurrent_executions = 100 # ← Critical!
}
`Result: Stopped $14k/month cost explosions during traffic floods.
5. Stateful Anti-Patterns
❌ Our mistake: Stored session data in Lambda memory.
✅ Fix: Shifted to DynamoDB DAX for microsecond state reads:
python
`
from boto3 import Session
session = Session()
dax = session.client('dax', region_name='us-east-1')
response = dax.get_item(TableName='Sessions', Key={'session_id': 'ABCD'})
`
Result: User session failures dropped to 0.02%.
Your Turn: What Serverless Nightmares Haunt You?
We've open-sourced our Serverless Post-Mortem Playbook with 30+ incident responses:
🔗 https://serverlesssavants.org/serverless-savants-aurora-serverless-cloud-computing/blog/
(Contains RCA templates, CloudWatch alarm configs & chaos testing scenarios)
Disclaimer: I'm part of the ServerlessSavants.org core team. All tools/resources we share are free (no paywalls).
Discussion starters:
What's your most savage serverless failure?
Any other observability tools you'd recommend beyond X-Ray?
How do you balance cost vs. performance in production?
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