Serverless Architecture Services

Serverless (AWS Lambda) is well-suited to: event-driven workloads (process each SQS message, S3 event, or API call independently), variable or bursty traffic (scales from zero instantly, cost is zero when idle), and scheduled tasks (run a Lambda on cron instead of keeping an EC2 instance alive). Serverless is NOT well-suited to: long-running processes (Lambda has a 15-minute max execution timeout use ECS Fargate for anything longer), latency-sensitive applications where cold start is unacceptable (Lambda cold start adds 100ms-2s on first invocation Provisioned Concurrency mitigates this but adds cost), or stateful applications that maintain connections (database connection pooling is problematic with Lambda RDS Proxy mitigates this at additional cost). ClickMasters recommends the correct compute choice Lambda, ECS Fargate, or EC2 based on the specific workload characteristics, not as a blanket preference.

Lambda cold start occurs when AWS must initialise a new execution environment for a Lambda function that has not been invoked recently downloading the deployment package, starting the runtime, and executing the initialisation code outside the handler. Cold starts add 100ms-2s of additional latency on the first invocation after an idle period. For Node.js Lambda functions with small packages: cold starts are typically 100-300ms acceptable for non-latency-sensitive APIs and background processing. For Node.js with large packages, or Python/Java runtimes: cold starts can be 500ms-2s potentially unacceptable for user-facing APIs. Mitigations: Provisioned Concurrency (pre-warm a number of Lambda instances guaranteed sub-millisecond start), code optimisation (reduce package size, defer heavy initialisation), SnapStart (Java snapshot initialised environment, 90% cold start reduction), and Graviton2/ARM64 (20% cheaper, 19% better price-performance). For user-facing APIs where cold start is a concern, ECS Fargate (no cold start) is often the correct choice over Lambda.

Standard Workflows are designed for long-duration, exactly-once execution with durable state. Use when: workflow duration >5 minutes (up to 1 year), exactly-once execution is required (audit/compliance), you need retry with exponential backoff and fallback states, or you need full execution history for compliance. Express Workflows are designed for high-volume, short-duration workflows with at-least-once execution. Use when: workflow duration <5 minutes, high-volume (thousands per second), cost sensitivity (Express is cheaper per state transition), or idempotent workloads where duplicate execution is acceptable. ClickMasters uses Standard Workflows for business-critical processes and Express Workflows for high-throughput event processing.