What we look for before touching legacy infrastructure

Rebuilding legacy infrastructure is expensive and risky, so we start from the assumption that it shouldn't happen unless one of three specific conditions is present.

First: the system can no longer be safely changed — every fix introduces a new bug elsewhere. Second: the system can't scale to meet real, near-term demand. Third: the system creates a compliance or security exposure that can't be patched around.

If none of those three are true, the better investment is usually incremental — better monitoring, targeted refactors, and documentation, not a rebuild. Most 'we need to rebuild this' conversations are actually 'we don't understand this system anymore' conversations, and those have a cheaper fix.

When a rebuild genuinely is justified, we phase it against the live system rather than running a parallel big-bang cutover — slower, but it means the business never stops operating while the new system is proven out.