What is provisioned concurrency in AWS Lambda?

Provisioned Concurrency is an AWS Lambda feature that pre-initializes a specified number of execution environments and keeps them warm indefinitely, eliminating cold starts for those environments. When a request comes in, it's immediately handled by a pre-initialized instance without any initialization delay. Configuration: you allocate provisioned concurrency at the function alias or version level — aws lambda put-provisioned-concurrency-config --function-name myFunc --qualifier LIVE --provisioned-concurrent-executions 10. Pricing: provisioned concurrency is billed at ~$0.000015/GB-second for the pre-warmed capacity, plus the standard execution cost. Use cases: latency-sensitive APIs (payment processing, real-time recommendations), JVM/Java functions with notoriously long cold starts (2-5 seconds), high-traffic periods (auto-scale provisioned concurrency with Application Auto Scaling based on schedule or metric). Caveat: provisioned concurrency doesn't help beyond its configured count — requests above that level still experience cold starts.