On "cloud" servers we usually see that when disk I/O stops being the bottleneck (given enough disk I/O you can account for small amounts of RAM). So I'd guess t

On "cloud" servers we usually see that when disk I/O stops being the bottleneck (given enough disk I/O you can account for small amounts of RAM). So I'd guess their disk setup had some capacity left when they upgraded or they just have a lot of reads and the data fits in memory