Modernising what you already run
The rewrite always looks worse than the strangler. A staged migration keeps the thing that works while you replace the thing that does not.
The instinct when a system gets painful is to rewrite it. Rewrites fail for a boring reason: they swap a working system for a half-working one, and you carry both for longer than anyone budgeted. The alternative that keeps working is to leave the thing alone until its replacement is genuinely ready.
Put a seam in front of the old system
Most legacy systems are hard to replace and easy to wrap. Put a real interface in front of it, move one capability at a time behind that interface, and every step is independently reversible. You are not rewriting; you are changing what is behind the wall.
Find the capability that hurts, not the code that is ugly
Ugly code that works is cheaper than clean code that does not. Replace the thing that costs you incidents or on-call hours, not the thing that offends the eye. Modernisation runs from $899 and starts with that conversation, not with a diagram.
Do not rewrite the data layer twice
Most painful migrations are data migrations, and most of those fail because two systems briefly disagreed about the truth. Make one side authoritative at every step, backfill rather than dual-write wherever possible, and make the reconciliation routine something you run rather than something you hope about.
Data pipelines from $1,299 are usually the boring work that makes everything else possible — schemas that are enforced, loads that are idempotent, and a warehouse where the numbers reconcile.
Dashboard the thing you are deciding about
Part of what makes a legacy system expensive is that nobody can see what it is doing. Analytics dashboards from $799 answer specific questions — is the pipeline healthy, which customers are churning, what did that deploy change — rather than displaying every number available.
Document it while you are in there
The reason nobody wants to touch the system is that nobody knows how. Developer documentation from $699 is not glamorous, and it is the single highest-leverage thing in most modernisation engagements, because it is what makes step three possible.