We'll be migrating various servers to newer ones over the next day or two. Users can expect some brief disruption, for example new shortened URL creations might be disabled for a few minutes.
We'll try to keep any such issues to a minimum, but as we're moving to much newer software and hardware, there is a chance of unforeseen problems. I will be monitoring things closely and troubleshooting any issues that might arise.
Update: This work has now been completed, without any unexpected problems.