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4.5.2. Quick Reference: Key Limits & Defaults
| Service | Limit / Default | Exam Relevance |
|---|---|---|
| Lambda timeout | Default 3s, max 900s (15 min) | Timeout errors → check this first |
| Lambda memory | 128 MB – 10,240 MB | More memory = more CPU = faster |
| Lambda /tmp storage | 512 MB (up to 10 GB) | Ephemeral — cleared between invocations |
| Lambda deployment package | 50 MB zipped, 250 MB unzipped | Use layers for large dependencies |
| Lambda concurrent executions | 1,000 (default, per region) | Reserved concurrency isolates functions |
| API Gateway timeout | 29 seconds (hard limit) | Lambda must finish within this |
| API Gateway payload | 10 MB | Large files → S3 presigned URLs |
| DynamoDB item size | 400 KB max | Large items → store pointer to S3 |
| DynamoDB partition key | Required for every table | Determines data distribution |
| DynamoDB LSI | Must create at table creation | Cannot add later (vs. GSI anytime) |
| SQS visibility timeout | Default 30s | Must exceed Lambda processing time |
| SQS message retention | Default 4 days, max 14 days | Messages deleted after retention |
| SQS FIFO throughput | 300 msg/s (3,000 with batching) | Lower than Standard (unlimited) |
| SNS message size | 256 KB | Large payloads → S3 reference |
| S3 object size | 5 TB max (5 GB single PUT) | >5 GB → multipart upload |
| CloudWatch Logs retention | Never expires (default) | Set retention to control costs |
Written byAlvin Varughese•Founder•15 professional certifications