What is the primary benefit of AWS Lambda?

Correct answer: Pay only for the compute time you consume

Option D is correct because AWS Lambda uses a consumption-based pricing model in which customers are billed only for the number of requests and the duration of compute time their functions actually consume, measured in milliseconds, resulting in zero cost when no functions are running. Option A is incorrect because Lambda does not provide automatic database scaling; services like Amazon Aurora Serverless handle database scaling separately. Option B is incorrect because Lambda does not offer a standalone 99.99% uptime SLA as a primary benefit, and availability guarantees are distinct from its core serverless value proposition. Option C is incorrect because Lambda does not include built-in load balancing; routing and load distribution are handled by other services such as API Gateway or Application Load Balancer.