GuideAdvanced
Modernizing Legacy Systems with ROI Guide
Every old system that nobody wants to touch costs money, even if it never shows up on an invoice: what it costs to keep it running, the risk that it fails, and what the business can't launch because changing it takes months. This guide teaches you to treat legacy as an investment decision instead of a technical complaint: inventory what it costs, see technical debt as a portfolio, choose part by part between keeping, encapsulating, replacing incrementally or rewriting, build the business case with its ROI calculated by hand, sell it to leadership and finance, separate what AI agents really make cheaper from what they don't, plan the migration without stopping the business, and know when to stop. You learn it as Head of Engineering at **Banco Ceiba**, a regional Colombian bank with 1.8 million customers, a COBOL core on a mainframe since 1988, and a modern mobile app on top. A systems integrator offers to migrate everything in 18 months "with AI agents," and the CEO asks in the leadership meeting: "Can AI migrate everything now?" Module by module you build the answer: a legacy cost sheet, a debt portfolio, an options matrix, a business case, an investment memo, an AI assumptions register, and a roadmap with decision gates. There is no code to write and you don't need to know COBOL. The math (cost, net present value, payback, sensitivity) is done in tables and by hand, and every source comes with its date.
- lessons
- 64
- modules
- 8
- available in
- English · Spanish
- access
- Free
What you'll be able to do
- Inventory a legacy system and calculate what it costs: keeping it running, its risk, and its opportunity cost
- Treat technical debt as a portfolio, with principal and interest by domain, and decide which debt to pay and which not
- Choose per domain between keeping, encapsulating, replacing incrementally, or rewriting, with explicit criteria
- Build the business case for a migration and calculate its ROI, payback, and net present value by hand
- Sell the investment to leadership, finance, and the risk committee, and answer a "migrate everything" offer
- Separate what AI agents make cheaper in a migration from what they don't, and the new risks they bring
- Plan the migration in phases without stopping the business, with decision gates and criteria to stop
- Deliver the full modernization plan and defend it in front of the board
What you need to bring
It's for you if...
- Tech leads and architects who lead teams and live with a system nobody wants to touch
- Engineering managers, directors, and heads of engineering who need to ask for budget to modernize
- CTOs and technical founders who receive "migrate it all with AI" offers and have to decide
Requirements and materials
- Having worked with or near a legacy system
- No COBOL, mainframe, or finance background needed: every term is explained the first time
The syllabus, module by module
Open any of them to see its lessons.
What people usually ask
No limit. It's a free guide: come in whenever you like, as often as you like.
No. Modules run from easier to harder, but you can jump to the one you need. Progress is saved per lesson.
Whatever is needed is listed under “What you need to bring”, above. If nothing is listed there, you can start from zero.
In the WhatsApp group, and every two weeks there's a live with an instructor where questions get worked through.
Start whenever you like
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