[SethTro]

The article doesn't say it anywhere but I sure hope all the games are backed up to disk/tape in txt format and that this is just used to keep in-memory DB/memcache size down.

Otherwise an interesting article about injecting domain knowledge to improve beyond what's possible with a normal compression algorithm.

[apetresc]

Indeed, you can download this backup yourself if you'd like: https://database.lichess.org/