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Guide

How to modernize a legacy app

Follow these steps in Evonx to incremental modernization PRs that reduce risk compared to big-bang rewrites.

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Step-by-step

Inventory constraints

Framework versions, deployment model, and modules that must not break.

Pick a vertical slice

One screen or API route to upgrade first with measurable value.

Add characterization tests if missing

Lock current behavior before structural refactors.

Modernize UI or API layer

Upgrade components or endpoints while keeping data contracts stable.

Preview with stakeholders

Use Evonx previews to validate parity before merge.

Schedule next slice

Repeat per module; track debt paydown in evolution threads.

Outcome

Incremental modernization PRs that reduce risk compared to big-bang rewrites.

Related resources

How to build a CRMFollow these steps in Evonx to a working CRM repository with leads, accounts, opportunities, and activities you can prevHow to build a SaaSFollow these steps in Evonx to a multi-tenant SaaS codebase with organizations, roles, and billing integration hooks.How to build a customer portalFollow these steps in Evonx to a secure portal where customers manage profile data, tickets, and documents.How to add features to an existing appFollow these steps in Evonx to new functionality merged into a live codebase with reviewable diffs.How to build an HR systemFollow these steps in Evonx to a working HR repository with employees, leave, and org structure you can preview and shipHow to build a POS systemFollow these steps in Evonx to a point-of-sale app with catalogs, carts, and tender flows you can preview and ship. Pair

FAQ

Do we need a big-bang rewrite?

Usually no. This guide prefers slice-by-slice modernization with parallel running and reconciliation checks.

What if documentation is missing?

Treat observed behavior and data as the spec; flag ambiguities for human confirmation instead of inventing rules.

How does this connect to Evonx existing-software pages?

Those pages own commercial positioning. This guide owns the stepwise modernization checklist.

Build production software with Evonx

Start from a template or connect an existing repository. Evonx helps you ship real applications with preview, evolution threads, and pull-request delivery—not disposable demos.

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