Situations to reason through: a failing rewrite, a vendor lock-in, a security mandate, a merged codebase.
3 questions in Architecture & Tech Leadership.
Establish what the product is load-bearing for and what the deadline really is once procurement, security review and change freezes are subtracted, then price four options against that calendar: pay for an extension, move to the vendor's successor, replace it, or absorb the capability.
Find out why it happened before deciding what to do about it, because duplication is usually a symptom of a discovery or ownership failure that consolidation alone will not fix. Then choose deliberately between merging, keeping both, and letting one wither, on the basis of migration cost rather than tidiness.
Spend the first week building an evidence map from money, traffic, incidents and deploys rather than from code, and interviewing the people who touch it with one fixed set of questions. Spend the second producing a risk-ordered plan of stabilisation before structure, with unknowns listed explicitly.