There are zero reasons to limit yourself to 1GB of RAM. By paying $20 instead of $5 you can get at least 8gb of RAM. You can use it for caches or a database that supports concurrent writes. The $15 difference won’t make any financial difference if you are trying to run a small business.

Thinking about on how to fit everything on a $5 VPS does not help your business.

NVME read latency is around 100usec, a SQLite3 database in the low terabytes needs somewhere between 3-5 random IOs per point lookup, so you're talking worst case for an already meaningful amount of data about 0.5ms per cold lookup. Say your app is complex and makes 10 of these per request, 5 ms. That leaves you serving 200 requests/sec before ever needing any kind of cache.

That's 17 million hits per day in about 3.9 MiB/sec sustained disk IO, before factoring in the parallelism that almost any bargain bucket NVME drive already offers (allowing you to at least 4x these numbers). But already you're talking about quadrupling the infrastructure spend before serving a single request, which is the entire point of the article.