What was the cost? It appears to be latency, but apparently not of the crippling sort, though we don’t have benchmarks. In any case, Google thought dealing with latency was an easier task than programmers hacking around the lack of transactions. I find that just fascinating. It brings to mind so many years of RDBMS vs NoSQL arguments it’s not even funny.
more on highscalability.com
Analysis of Google’s paper on their new database, Spanner.