I followed this line of thinking last week due to curiosity w.r.t ECS & SQLite. I found that the bottleneck was not on the reads, but on the complexity of the writes (iterating each entity and subsequently you have num_systems X num_components writes). You can actually avoid this entirely if you write your systems in SQL.

Since I had already thrown out logic & reason for the sake of curiosity, I took it a step further and learned that the Bun JS runtime actually has SQLite baked in, which allows you to create a :memory: db that can be accessed _synchronously_ avoiding modification of most ECS implementations. (I'm not familiar with the larger SQLite ecosystem, but being a largely TS developer this was very foreign to me)