They released this tool a couple of years ago <a href="https:&#x2F;&#x2F;stripe.com&#x2F;blog&#x2F;announcing-mosql" rel="nofollow">https:&#x2F;&#x2F;stripe.com&#x2F;blog&#x2F;announcing-mosql</a><p>In the post they wrote<p>&quot;Here at Stripe, we use a number of different database technologies for both internal- and external-facing services. Over time, we&#x27;ve found ourselves with growing amounts of data in MongoDB that we would like to be able to analyze using SQL. [...] MoSQL does an initial import of your MongoDB collections into a PostgreSQL database, and then continues running, applying any changes to the MongoDB server in near-real-time to the PostgreSQL mirror&quot;.<p>So they could have been run that migration on MongoDB.