One approach may be to tokenize user information. Ensure that any personal data is separated from other data and mapped via tokens and kept in one place. Handle

One approach may be to tokenize user information. Ensure that any personal data is separated from other data and mapped via tokens and kept in one place. Handle backups of this database with special care. You can then have the rest of your systems work as normal. All this is easier said than done if you have a large investment in existing systems, but it is probably a design approach you can enforce from the beginning if you are a startup.