Event-Driven Order Processing at Scale with Lambda & SQS
An e-commerce operator processing 50k+ orders/day needed a resilient, cost-efficient backend. We designed an event-driven architecture with Lambda, SQS dead-letter queues, and SNS fan-out, deployed with CDK infrastructure-as-code.
Processing cost reduced vs. prior ECS cluster
High availability over 6 months post-launch
Full CDK IaC — infrastructure reproducible rapidly
01The Challenge
The client ran order processing on a continuously running ECS cluster — paying for compute regardless of traffic, with no graceful spill-over at peak. The architecture had no dead-letter queue, meaning failed payment events were silently dropped. Infrastructure lived only in console-click history with no reproducible definition.
02Our Approach
We architected an event-driven pipeline: an API Gateway → Lambda ingest function published each order to SQS. A processing Lambda consumed the queue with configurable concurrency, with a DLQ capturing any failures for replay. SNS fan-out routed fulfilment, notification, and analytics events to dedicated consumers. The entire stack was defined in AWS CDK TypeScript — no click-ops, fully reproducible. Load testing confirmed stable throughput at 3× normal peak.
03Technologies Used
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