Fintech Core Migration
Decomposition of a legacy Node.js monolith into domain-driven serverless functions.
High-frequency trading desk requiring sub-second execution logs.
The monolith was single-point-of-failure. One bad deployment took down the entire trading floor.
Constraints
- Data consistency is non-negotiable (financial ledgers).
- Cannot pause trading for maintenance windows.
- Compliance logging for every API interaction.
- Strict AWS IAM permission boundaries.
Architecture
System designed for isolation. Auth, Core, and Analytics scale independently based on load profiles.
Engineering Decisions
Event-Driven Architecture
Decoupled transaction ingestion from processing using EventBridge. This ensured we never lost a trade, even if the processor crashed.
DynamoDB Single Table Design
Optimized access patterns for 'GetAccountHistory'. reduced query latency to single-digit milliseconds.
Infrastructure as Code
Everything Terraform. No manual console clicks. Allowed us to spin up ephemeral staging environments per PR.
Frontend & UX Intent
[ UI_SNAPSHOT_PLACEHOLDER ]
Internal admin tools rebuilt with Vite + React Query. Moved from stale-while-revalidate to real-time websockets for trade monitoring.
Outcome & Reflection
A resilient, auto-scaling ledger system.
System can now handle 10x volume without manual intervention.
I underestimated the cold-start times of Lambdas inside VPCs initially. Had to implement provisioned concurrency which increased costs slightly.