4.3.1 Define Concurrency
Define Concurrency
Lambda Concurrency Types
| Type | Mô tả | Cold Start |
|---|
| Unreserved | Shared pool (account default 1000) | Yes |
| Reserved | Guaranteed + capped for function | Yes |
| Provisioned | Pre-initialized containers | No |
Concurrency = Invocations/second × Average duration (seconds)
Example: 100 req/s × 0.5s = 50 concurrent executions
Key Rules
- Account default: 1000 concurrent
- Reserved = 0 → function disabled
- Throttling →
429 TooManyRequestsException - Burst: 500-3000 (region dependent)
- Unreserved pool = Account limit - all reserved
| Scenario | Type |
|---|
| Default | Unreserved |
| Critical function | Reserved |
| Eliminate cold starts | Provisioned |
| Disable function | Reserved = 0 |
Exam Tip: Reserved = guarantee + cap. Provisioned = no cold starts ($). Reserved = 0 disables function. Account limit shared across all functions.