For engineers in legacy code: modernize incrementally, no big-bang rewrite.
Reach for this when you inherit a business-critical codebase that has to keep running while you drag it onto a modern stack. Plan a strangler-fig migration that runs old and new side by side, carve one safe bounded-context seam out of a monolith, drive major framework and language-version upgrades as small reversible CI-gated PRs, recover the business rules buried in tangled code, pin current behavior with characterization tests before you touch it, audit dependency risk as you upgrade, and delete dead code with evidence — so nothing breaks while everything moves.
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Arranged in the author's recommended order. Walk through them in sequence, or open any one on its own.