In 2012, I worked on a nine month project to migrate a fairly large hot dataset (10s of TBs) off of SimpleDB and onto Riak. At the time, we were experiencing tens of hours of downtime a quarter, much of which could be attributed to SDB.
My favorite story about that migration is that four months into the project, we were moving along nicely and ready to start cutting over to Riak after the Christmas holiday. My office had decided to go out to lunch our last work day before everyone headed off for the holidays, and I received a call from a SDB support team member informing me that we either needed to move off their platform by Christmas Day or they'd have to shut us off (we'd start degrading other customers). Fortunately we were nearly ready to pull off the cutover, so we quite literally cut all of our traffic over on Christmas Eve (one of our busiest days of the year).
Over the upcoming years, our database continued to grow and grow, and all the while Riak trucked along. It wasn't always a smooth road, and we certainly had our challenges from time to time, but I have yet to hear of anyone who has used a massive 100TB hot database and not had to do work and maintenance.
Throughout the years I used Riak, it served me very well. I'm grateful to the innovative work so many at Basho created during their tenure, and I'm glad to see Bet365 attempt to steward the project to a new phase of its life. If I could toast every last basho employee, I would. Thank you all!