Rescuing a Legacy System Before It Collapsed
A critical business system was failing regularly and the original developers were long gone. We stabilized it, documented it, and set up a path forward.
Key Results
System uptime improved from 94% to 99.9%
Response times reduced by 70%
Complete system documentation created
Clear modernization roadmap delivered
The Challenge
A healthcare organization depended on a critical system built over a decade ago. The original developers had left years ago, documentation was nonexistent, and the system was failing with increasing frequency.
The team was afraid to make changes because they didn’t understand the codebase. But the failures were affecting patient care coordination.
Our Approach
Phase 1: Stabilization (2 weeks)
Before trying to understand everything, we focused on stopping the bleeding:
- Added comprehensive logging to identify failure patterns
- Implemented basic monitoring and alerting
- Fixed the most critical bugs causing outages
- Added database connection pooling (a major stability issue)
Phase 2: Understanding (3 weeks)
With the system stable, we could take time to understand it:
- Traced code paths for all major functions
- Documented the database schema (previously undocumented)
- Identified dependencies and integrations
- Mapped business logic to code
Phase 3: Documentation and Handoff (2 weeks)
We created documentation that would actually help:
- Architecture overview with diagrams
- Runbooks for common issues
- Developer onboarding guide
- Modernization roadmap with prioritized recommendations
The Outcome
The system went from 94% uptime to 99.9%. Response times dropped by 70% after we addressed the performance bottlenecks we discovered during documentation.
More importantly, the internal team now understands the system. They can make changes with confidence and have a clear path toward eventual modernization.
Technical Details
- Original Stack: PHP 5.6, MySQL 5.5, Apache
- Quick Wins: Connection pooling, query optimization, caching layer
- Monitoring Added: Prometheus, Grafana, PagerDuty integration
Key Takeaways
- Stabilize before understanding: Don’t try to rewrite while the house is on fire
- Logging is your friend: You can’t fix what you can’t see
- Documentation is deliverable: It’s not extra—it’s essential
- Small fixes, big impact: The 80/20 rule applies to legacy systems too
"We were afraid to touch the system because nobody understood it. Now we have confidence to maintain and eventually replace it."
IT Director
Healthcare Organization
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