Consider the example from the post of searching your shell history. If I don't need indexes I can just have it all in one flat file and use grep. Switching to a tool that supports indexing adds a lot of potential complexity and ways things could go wrong.
Or consider the example of a developer querying frontend logs: queries are many orders of magnitude less common than writes, and (at the scale I used to work at) an index would be incredibly expensive.
I take the point of your examples as written in the post, but I think both of those are a bad comparison to the Reddit Premium subscriber table being discussed, because:
- We’re already using a database, so there’s very minimal added complexity
- This is an extremely hot table getting read millions of times a day
- The scale of the data isn’t well-bounded
- Usage patterns of the table are liable to change over time
It wasn't an extremely hot table, and the scale of the data was well-bounded insofar as the only way for it to become non-negligible would be for us to have had revenue beyond our then-wildest dreams.
Or consider the example of a developer querying frontend logs: queries are many orders of magnitude less common than writes, and (at the scale I used to work at) an index would be incredibly expensive.