Case Study

Legacy Monolith to Modular Architecture

Systematically breaking down an aging monolithic application into maintainable, modular components using the Strangler Fig pattern to improve developer velocity.

Role
Staff Engineer
Timeline
12 Months
Industry
E-Commerce / Legacy Systems
Focus
Python

Problem Breakdown

The core monolith had become a bottleneck, where a single change could break unrelated features, and new features took weeks to develop due to heavy technical debt.

Architecture Decisions

  • /Gateway-level routing to divert traffic to new modules
  • /Shared database migration for incremental data extraction
  • /Modular monolith approach before moving to fully independent services

Trade-offs

  • ¬Overhead of maintaining dual architectures during transition
  • ¬Database synchronization challenges between monolith and new modules
  • ¬Slower initial progress to ensure zero-regressions on legacy paths

Key Outcomes

  • Successfully extracted 3 core business domains into independent modules.
  • Reduced the severity and frequency of regression bugs by 40%.
  • Increased developer onboarding speed and overall feature delivery velocity.
  • Improved system testability and enabled independent scaling of busy modules.
PythonDjangoPostgreSQLFastAPINginx

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