In my experience, in a multiuser environment SQLite falls over pretty hard, due to a lack of anything like MVCC. I'm aware that there a bunch of sqlite-compati

In my experience, in a multiuser environment SQLite falls over pretty hard, due to a lack of anything like MVCC. I'm aware that there a bunch of sqlite-compatible implementations and extensions that add MVCC. How close are those to actually being SQLite? Are they just a totally different table storage and transaction engine sitting behind SQLite's SQL parser/compiler and VM?