Choosing the right concurrency control

Lambda offers two concurrency controls that serve different purposes. Reserved concurrency sets a hard cap on the maximum parallel executions for a function, protecting downstream resources from overload. Provisioned concurrency pre-initializes a specified number of execution environments so they are warm and ready, eliminating cold-start latency for latency-sensitive workloads.

Understanding when to apply each control is essential for balancing cost, performance, and reliability.