title: Azure SQL tables become slow when not queried for some time
body: <p>We use AzureSQL for storing tracing data for a number of processes in our application. These trace lines are in a flat table (no foreign keys etc.). We have grouped those trace line per month (we have a table for september, a table for october etc.), all within the same AzureSQL database. (not starting an Azure Table vs AzureSQL discussion here ;-)). At the beginning of next month, the trace data of previous month is processed for some reports. This works fine.</p>
  <p>What we notice, is that tables which are not queried for a week(?), those seem to be archived or something like that (cold storage?). If I run a simple SELECT COUNT(*) without where clause on a table of a month ago, that can easily take up 10-15 minutes for ~2M records. If we run the query from code (.net core in our case), there is an exception with an empty message thrown which behaves like an SQL-timeout. It seems that a warmup of the table (or data?) is present, because once we have ran our first query, sequential queries run fast again.</p>
  <p>Did we miss something? We're pondering on creating a support ticket at Microsoft, but I thought I'd ask first here.</p>