I had never read any papers on shadow paging when I wrote LMDB. I refer to it as double-buffering in the original LMDB paper because of my own prior experience

I had never read any papers on shadow paging when I wrote LMDB. I refer to it as double-buffering in the original LMDB paper because of my own prior experience writing graphics code. You can find the (L)MDB paper here https://openldap.org/pub/ https://openldap.org/pub/ Other commenters noting that append-only isn't efficient enough for general use are correct. We found this as well in the early days of testing LMDB with append-only behavior; 99% of pages were obsolete after only 5 transactions. That's why LMDB is CoW but not append-only, and that's why it uses a double-buffered meta page. Bzero's work on append-only Btree was educational and illuminating, but not usable in the real world.