We have been regularly observing degraded performance of the database for a little while. We intend to try and add indices to improve overall performances of some queries that make the database choke.
Since there is a considerable amount of data to process, and we also want to do some testing related to the changes, we plan on having the website down for at most 2 hours.
We apologize for the inconvenience.
EDIT 11:04pm : Maintenance over. It was way much faster than we thought it would to generate the index. We are going to generate only a few at a time and monitor over a few days to see if everything goes well.