How do you ensure seamless interoperability between legacy systems and new technology solutions?

My experience with blending legacy systems and new technology is to use a middleware to integrate the two.

With middleware integrations, there are a few best practices that I support:

1. Limited admins. Have you been in a system where every user is an admin? Seamless integrations are the big reason (especially if you receive pushback on limiting administrator access to tools) to limit who has access to adjust back end settings in a system. Well-meaning people can disrupt integrations by "just adding a field" or "updating the picklist values". (In full disclosure, have unintentionally disrupted systems by being given unnecessary admin access to them)

2. Document the integration. I'm a big fan of a data dictionary that identifies the system, field type, type of integration (single or bi-directional) etc. that is maintained as a living document among tech teams. I also live in the real world. So, within systems, update field descriptions to identify if they're used in integrations. Specifically identify the system and the direction of the sync in the description. From there, you can discuss with integration teams where the particular field maps to in other systems. And, in any tech debt reconciliation projects, you know which fields need special consideration.

3. Ensure that integration discussions are part of the discovery process for new projects. Does a project impact an existing integration? Does a new integration field/process need to be put together? Which system is the system of record? How does the integration support the solution proposed for the project?
   
   Project Managers or Business Analysts don't have to be highly technical to work with integrations, but should have a list of questions to ask when integrations are involved so the solution can support the user experience and data integrity.