Legacy System Modernisation Lessons Learned
This is a practical guide to building a lessons learned for a legacy system modernisation project — what went well and badly, captured to improve future projects, adapted to the realities of modernising or replacing ageing core systems.
What a Lessons Learned is
A lessons learned is what went well and badly, captured to improve future projects. For the full concept and how it works in general, see Lessons Learned. On a legacy system modernisation project it plays the same role, tuned to this kind of work.
Why it matters for a Legacy System Modernisation project
Legacy System Modernisation projects live or die on modernising or replacing ageing core systems. A well-built lessons learned gives the team a shared, explicit reference for exactly that — reducing ambiguity, aligning stakeholders, and making problems visible early enough to act. Skipping it, or doing it generically, is how legacy system modernisation projects drift into avoidable delay and cost.
What to include
- What happened
- Impact
- Root cause
- Recommendation
Legacy System Modernisation-specific considerations
Tailor the lessons learned to the risks that most often derail legacy system modernisation projects:
- Undocumented legacy behaviour
- Phased cutover risk
- Knowledge loss
Example
On a real legacy system modernisation project, the lessons learned would be shaped by modernising or replacing ageing core systems. In particular, it should explicitly account for the project’s biggest risks — undocumented legacy behaviour, phased cutover risk, knowledge loss — rather than treating them as afterthoughts.