I’ve worked on several projects with sqlite, both read and write heavy, all with high concurrency, with databases in the few hundred MB with 400k server clients, and 100 bare-metal servers running at capacity. The sqlite part of our system is never the problem. In our case sqlite has been an alternative to custom files on disk or replacing a spaghetti of hashmaps in memory. we also replaced a single postgresql instance with all customers into many sqlites per customer. Performance and reliability is why I always reach for it first. At this point I’m a zealot and would argue your first ‘data structure’ of choice should be an sqlite database :)