Lock-in is a data question
Founders talk about vendor lock-in as if it were about code. Code is the easy part: it can be rewritten, and the rewrite gets cheaper every year. The part that cannot be rewritten is the data - the customer records, content, files and history your product accumulates every day it runs. When a tool is hard to leave, it is almost always because the data is hard to move. So evaluate every tool you adopt with one question before any other: when I leave, what exactly comes with me?
Inventory before you integrate
Before connecting a new service, list the kinds of data it will hold. Customer accounts and profiles. Content your users create. Uploaded media. Configuration and settings. Analytics and event history. For each one, note where it will live and who controls the credentials that reach it. This inventory takes fifteen minutes and changes decisions: a tool that will hold only throwaway cache needs no exit plan, while the one holding your customer table needs a good one.
Formats decide whether an export is useful
Every vendor can truthfully say "you can export your data." The question is what the export contains. A CSV of rows is useful. A JSON dump of internal IDs that reference files you cannot download is not. Before you depend on a tool, check three things: the export format, whether attached media and files come along or only their references, and whether the export is self-service or requires a support request. If the answer to that last one is "email us", assume the export will arrive slowly at exactly the moment you need it fast.
Read the terms for the ending
Terms of service are mostly about how a relationship works, but the clauses that matter most here are about how it ends: how long the vendor keeps your data after you cancel, whether deletion is immediate or on a delay, and what happens if the vendor itself shuts down. Where your users are in the European Union, you also have a legal lever: Article 20 of the GDPR gives people a right to data portability for their personal data in a structured, commonly used, machine-readable format, which in practice pushes vendors toward real exports. Know the clause before you need the clause.
Test a restore, not just a download
The most common backup failure is not a missing export; it is an export nobody has ever opened. Schedule a drill, quarterly is enough for most early products: run the export, load it into a scratch environment, and verify that record counts and spot-checked entries match production. Only then do you have a backup. Until then you have a file you are optimistic about. The same drill doubles as your migration rehearsal: the day you actually switch vendors, it will be the second time you have done it, not the first.