Writing
Notes from building financial systems
Writing on backend engineering, lending and payment systems, distributed architecture and the performance work that keeps them fast. 8 posts, filterable below.
8 posts
Designing a Term Loan Engine That Product Can Reconfigure
Every new lending variant shouldn't be an engineering project. Notes on modelling interest, margin and moratorium as configuration rather than code paths.
- Lending
- Domain Modelling
- Python
Cutting Payment Turnaround From 30 Minutes to 2
The bottleneck was almost never the payment rail. A walk through decoupling processing from the request cycle, and making retries safe enough to be aggressive.
- Payments
- Celery
- Queues
RAG in Production: What Actually Breaks
Retrieval quality, not model choice, decides whether an internal knowledge assistant is trusted. Lessons from putting a RAG platform in front of real teams.
- RAG
- LLM
- Retrieval
Upgrading Django 2.2 to 5.2 Without a Feature Freeze
A staged approach to a multi-version framework upgrade across a live lending platform — and why the dependency graph is harder than the framework itself.
- Django
- Python
- Modernization
A Serverless OCR Pipeline That Handles Bursty Volume
Invoice documents arrive in unpredictable bursts. Notes on building an event-driven extraction pipeline where each stage scales on its own.
- AWS
- Lambda
- SQS
When Month-End Took 22 Hours
Batch jobs that outgrow their data volume fail slowly and then all at once. A practical order of operations for reclaiming hours from a nightly close.
- PostgreSQL
- Query Optimization
- Batch Processing
Event-Driven Architecture When the Payload Is Money
Queues and workers make systems responsive. They also make correctness harder. What changes when an at-least-once delivery moves real funds.
- Event-Driven
- Distributed Systems
- Idempotency
Reading a Loan Lifecycle as a State Machine
Origination, disbursal, servicing and closure are usually modelled as flags. Modelling them as explicit states removes a whole class of impossible bugs.
- Lending
- LOS
- LMS