Azure SQL - System.ComponentModel.Win32Exception: The wait operation timed out - azure-sql-database

Question

I have an MVC Azure Web App, using an Azure SQL Database.
I've just finished developing a new version on my local machine, and released it to my Azure test environment, but it's behaving a bit strangely: some parts of the system work, but one particular part (which hasn't changed for this release) is giving me the following error:
System.Data.SqlClient.SqlException (0x80131904): Execution Timeout Expired. The timeout period elapsed prior to completion of the operation or the server is not responding.
---> System.ComponentModel.Win32Exception (0x80004005): The wait operation timed out
at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
at System.Data.SqlClient.SqlDataReader.TryConsumeMetaData()
at System.Data.SqlClient.SqlDataReader.get_MetaData()
at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString, Boolean isInternal, Boolean forDescribeParameterEncryption)
at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async, Int32 timeout, Task& task, Boolean asyncWrite, Boolean inRetry, SqlDataReader ds, Boolean describeParameterEncryptionRequest)
at System.Data.SqlClient.SqlCommand.RunExecuteReaderTdsWithTransparentParameterEncryption(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async, Int32 timeout, Task& task, Boolean asyncWrite, Boolean inRetry, SqlDataReader ds, Boolean describeParameterEncryptionRequest, Task describeParameterEncryptionTask)
at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean& usedCache, Boolean asyncWrite, Boolean inRetry)
at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)
at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)
at System.Data.Entity.Infrastructure.Interception.InternalDispatcher`1.Dispatch[TTarget,TInterceptionContext,TResult](TTarget target, Func`3 operation, TInterceptionContext interceptionContext, Action`3 executing, Action`3 executed)
at System.Data.Entity.Infrastructure.Interception.DbCommandDispatcher.Reader(DbCommand command, DbCommandInterceptionContext interceptionContext)
at System.Data.Entity.Core.Objects.ObjectContext.ExecuteStoreQueryInternal[TElement](String commandText, String entitySetName, ExecutionOptions executionOptions, Object[] parameters)
at System.Data.Entity.Core.Objects.ObjectContext.<>c__DisplayClass69`1.<ExecuteStoreQueryReliably>b__68()
at System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess)
at System.Data.Entity.Core.Objects.ObjectContext.<>c__DisplayClass69`1.<ExecuteStoreQueryReliably>b__67()
at System.Data.Entity.Infrastructure.DbExecutionStrategy.Execute[TResult](Func`1 operation)
at System.Data.Entity.Core.Objects.ObjectContext.ExecuteStoreQueryReliably[TElement](String commandText, String entitySetName, ExecutionOptions executionOptions, Object[] parameters)
at System.Data.Entity.Core.Objects.ObjectContext.ExecuteStoreQuery[TElement](String commandText, ExecutionOptions executionOptions, Object[] parameters)
at System.Data.Entity.Internal.LazyEnumerator`1.MoveNext()
at System.Linq.Enumerable.First[TSource](IEnumerable`1 source)
The part that's failing calls a stored procedure to generate some management information. It works fine in my local environment and on the production site, but fails in the test environment. In the environments that work, it takes a fraction of a second to run.
Other parts of the test system are working fine, and the performance is the same as usual.

Answer 1

It turned out that the problem was the pricing tier of the database.
Until now I've been running the test database at Basic level, to keep costs down. Basic level supports databases up to 2GB.
When I imported the most recent copy of the production database it was less than 2GB, so I was allowed to select Basic, but that didn't leave enough space for the temporary tables used by the stored procedure that was causing the problem.
As soon as I switched to the Standard pricing tier and increased the maximum size of my database to 5GB, the problem went away.