static void Main (string[] args)
{
    // Default resiliency settings (since .NET 4.5)
    var defaultConnectionString = "Data Source=localhost;Initial Catalog=EFIdleResiliencyBug1;Integrated Security=SSPI";

    // Retry Interval = 3s (instead of 10 which seems to be the default)
    var connectionStringThreeSeconds = "Data Source=localhost;Initial Catalog=EFIdleResiliencyBug2;Integrated Security=SSPI;ConnectRetryInterval=3";

    // Retry Count = 0 (instead of 1) => means Resiliency Feature is disabled.
    var connectionStringZeroRetry = "Data Source=localhost;Initial Catalog=EFIdleResiliencyBug3;Integrated Security=SSPI;ConnectRetryCount=0;";

    // Here we also create a default connection string but with a different db
    var defaultConnectionString2 = "Data Source=localhost;Initial Catalog=EFIdleResiliencyBug4;Integrated Security=SSPI";

    Drop(defaultConnectionString); // takes > 10s
    Drop(connectionStringZeroRetry); // Takes no time (connection resiliency disabled)
    Drop(connectionStringThreeSeconds); // takes > 3s
    Drop(defaultConnectionString2); // takes > 10s

    //All connection strings (same DbContext class) try to connect to the DB.
    Create(defaultConnectionString); // BUG: Takes 10s
    Create(connectionStringThreeSeconds); // BUG: Takes 3s
    Create(connectionStringZeroRetry); // Takes no time (connection resiliency disabled)
    Create(defaultConnectionString2); // BUG: Takes 10s (seems to be the default RetryInterval for some reason).

    // Note: When using a different derived class from DBContext for each connection string the bug does not exist.

    // Expected Behavior: Ignore connection resiliency for checking if the db exists. (It should not take 3s or even 10s).
    // This is especially a problem when executing integration / unit tests that drop the db at the beginning.
}

private static void Create(string connectionString)
{
    Console.WriteLine($"Creating {connectionString}");
    var sw = Stopwatch.StartNew();

    using (var dbContext = new TestDbContext(connectionString))
    {
        dbContext.Database.EnsureCreated();
        Console.WriteLine("Creating DB took: " + sw.Elapsed);
    }
}

private static void Drop(string connectionString)
{
    Console.WriteLine($"Droping {connectionString}");
    var sw = Stopwatch.StartNew();

    using (var dbContext = new TestDbContext(connectionString))
    {
        sw = Stopwatch.StartNew();
        dbContext.Database.EnsureDeleted();

        Console.WriteLine("Deleting DB took: " + sw.Elapsed);
    }
}

public class TestDbContext : DbContext
{
    private readonly string _connectionString;
    public TestDbContext(string connectionString)
    {
        _connectionString=connectionString;
    }
    
    protected override void OnConfiguring(DbContextOptionsBuilder options)
    {
        options.UseSqlServer(_connectionString);
    }
}