# How to get out of a legacy vendor system

> When a closed vendor system is slow and expensive to change, Substrait's team rebuilds the functions you use on Substrait, so you own the data and the software and later changes are fast.

URL: https://substrait.build/problems/replace-a-legacy-system/  
Last updated: 2026-11-06

**The question:** We depend on a closed legacy system that is expensive to change and barely connects to anything. How do we get out?

Rebuild what you use, on a platform you own. Substrait's team rebuilds the functions your people rely on, on Substrait, so you own the data and the software, and every later change and integration is fast.

## The cost of staying

The licence is the smaller cost of a closed vendor system.
With AI, a change to software is now fast to make.
A closed system holds back every improvement your own people could make, because only the vendor can change it, on the vendor's timeline and price.
Every integration with your other systems waits in the same queue.

## What Substrait does

Substrait's team rebuilds the system you want out of, on Substrait.
You own the data and the software.
Your people can build alongside the team, and keep improving the system after go-live.

| | The legacy system | Rebuilt on Substrait |
|---|---|---|
| Your data | In the vendor's system and format | Yours, in a system you own |
| A change request | A quote, then a wait | Your people, or Substrait's team, with no vendor queue |
| Your other systems | Little or no connection | Connected, with access the data owner approves |
| Who can improve it | Only the vendor | Your own people, on Substrait |

## Two checks before work starts

1. **Substrait rebuilds what you use.** The team maps the functions your people rely on, and promises those.
2. **The vendor holds nothing besides code.** If the vendor holds content rights, a supplier network or a regulatory approval, the team tells you before work starts.

## How it starts

1. Tell Substrait which system it is, and what it runs in your business.
2. Substrait's team maps the functions your people use, and how the system connects to the rest.
3. You get a plan: what is rebuilt, in what order, and the estimate.
4. The team builds it on Substrait, with your people alongside where they want to be.

## Questions and answers

### Do you rebuild everything the old vendor ships?

No. Substrait's team rebuilds the functions your people use, mapped with them, not every feature the vendor ships.

### Is there anything a rebuild cannot replace?

Yes. Some vendors hold more than software, such as content rights, a supplier network or a regulatory approval. A rebuild does not replace those, and Substrait's team checks for them before work starts.

### Who changes the system after go-live?

Your own people can, on Substrait, with the same security check and data grants as any other tool. Substrait's team can also make changes for you.

## Related

- [Solutions for every starting point](https://substrait.build/solutions/): Substrait serves three kinds of company: teams already building with AI, companies ready to start whose work still runs on spreadsheets, chat and paper, and companies stuck on a closed legacy vendor system. Each has its own way in.
- [Company data, granted by its owner](https://substrait.build/capabilities/governed-data-access/): A tool on Substrait reads company data only after the data owner approves it, for a set time, through one gateway that holds the credential, checks every call and records every read.
- [Agentic Builder: requests become tools](https://substrait.build/capabilities/agentic-builder/): Agentic Builder is the part of Substrait where anyone asks for a new tool or a change in plain words, and build agents plan, build, test and ship it under the company's own rules, with the tool's owner in charge.
- [Templates: Substrait's best practice, wired to your company](https://substrait.build/capabilities/seeded-templates/): Substrait builds templates of common business software on best practice from its own experience. Every installation starts with them, already connected to the company's cloud, sign-on, identity, data and design. A template is copied and owned, never locked to a central version.