Name the capability first
Describe what the organization needs to do better: release a product, answer a customer, recover from an outage, or process a transaction. Platform choices should support that capability rather than become the objective themselves.
Choose a measurable baseline
Record the current outcome before changing the system. Useful measures can include lead time, recovery time, workload cost, and task completion. Choose measures that fit the business and record the conditions under which they were collected.
Modernize in increments
Separate essential dependencies and pick a manageable change. Improve observability and release safety as you go. A large rewrite can create risk if it delays the first useful improvement or obscures where value is coming from.
Review the result
Compare the changed system with the baseline and inspect the tradeoffs. A service can become easier to operate while spending more; a cheaper deployment can reduce reliability. Decide deliberately which tradeoffs the business can accept.