We fixed that problem and deployed it. It turned out to be the iframe with the tutorial app. That sets a new hash with a random todo list id and that captures the back button. It was not intended to keep people on our site.

Thanks for pointing the issue out!

BTW, I agree, RDBMSs are a great choice if the hot data set fits in main memory and queries are well-optimized through appropriate indexes. Issues usually only start to occur if 1) the data set is too large 2) queries cannot be optimized by the query optimizer and involve full-table scans 3) interleaved transactions contend on few rows.