Transactional Billing System: Under 30-Day Financial App Development

In April 2024, we participated in a contract bid to develop a transactional billing system for a law firm. The project had a three-month deadline, already compressed due to delays in data warehouse integration. Though we weren't initially selected, by May 2024, the client returned with an urgent request - their chosen agency had made minimal progress, and they needed delivery within a month.

The inherited codebase had significant challenges:

  • Invalid assumptions were made about events' data structures
  • Full table scans were required for each operation
  • Implementation was a loosely connected collection of Python scripts

Given our timeline, we decided on dumping the code and building a new system. Our solution included:

  • Celery canvas-based infrastructure for incremental data ingestion
  • React frontend for invoice management and transaction verification
  • Django backend API for system operations

Throughout development, we maintained continuous communication with the client to ensure the shortest possible feedback loops. We implemented an incremental delivery approach, enabling the client to begin testing features as soon as they were ready. This proved crucial in meeting the aggressive timeline.

The project went live within our 30-day target. While we encountered some post-deployment issues, all were resolved within a week. The client achieved their business objectives, and we demonstrated our ability to deliver under pressure without compromising on quality.

This rapid delivery succeeded through pragmatic technical decisions, clear communication channels, and focused incremental development. The client achieved their objectives, and we demonstrated our ability to deliver quality work under pressure.

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