I have developed a Web Application a standard web application to allow users to display and update a set of data from an SQL database.
The Web Application uses a An
15 minutes is too short for your app to be recycled (as suggested by CSharpRocks). I dont think its the issue here.
The delay is because a new Db connection is established upon first call after idle timeout. Typically if a connection is inactive for 4-10 minutes it will be closed. If a minimum pool size is specified, those connections will be kept alive even after idle timout expires.
Try using this connection string (adjust min pool size as per your needs)
Further details Why do we need to set Min pool size in ConnectionString
List of SQL Connection Properties - documentation