We push Lambda, DynamoDB, and SQS to one million requests per second and share what breaks. Learn partition-aware DynamoDB design for extreme write throughput, Lambda concurrency shaping to prevent downstream crush, SQS as a backpressure buffer with adaptive batching, and retry amplification math that turns a blip into a cascade. We present real numbers: cold start budgets at scale, the exact crossover point where serverless cost exceeds containers, and the operational trade-offs at each threshold.