Azure Cosmos DB Connection Slow

Question

I am finding connecting to and querying Azure Cosmos DB with C# .Net is very slow. It is taking about 2.5 seconds to connect and 8 seconds to do a simple query returning about 600 rows (no where clause). Is there more efficient way to do this? Or best to use a client side connection pool so connections are re-used so don't have to connect as many times? This will mainly be used as a Azure Web Service (ASP.Net)

Interesting if I don't do the ReadThroughputAsync() method after getting the cosmos container, then the Initialize() only takes 438 ms but the query takes longer (8.9 seconds). Anyone know why this is?

With calling await _container.ReadThroughputAsync():
    Initialize() in 2482 ms
    Found 598 results in 8171 ms

Without calling await _container.ReadThroughputAsync():
    Initialize() in 438 ms
    Found 598 results in 8937 ms

private const string ContainerId = "Items";
private const string DatabaseId = "Results";
private const string EndpointUri = "https://myServer.documents.azure.com:443/";

private const string PrimaryKey ="xxxxxxx==";

private Container _container;
private CosmosClient _cosmosClient;

private Database _database;

public async Task Initialize()
{
    var tickCount = Environment.TickCount;
    _cosmosClient = new CosmosClient(EndpointUri, PrimaryKey,
    new CosmosClientOptions {ApplicationName = "DataImporter"});
            _database = _cosmosClient.GetDatabase(DatabaseId);
    
    _container = _database.GetContainer(ContainerId);
    
    var throughput = await _container.ReadThroughputAsync();
    
    tickCount = Environment.TickCount - tickCount;
    WriteLine($"Initialize() in {tickCount} ms");

    var tickCount2 = Environment.TickCount;
    var sqlQueryText = $"SELECT * FROM c";
    var queryDefinition = new QueryDefinition(sqlQueryText);
    var queryResultSetIterator = _container.GetItemQueryIterator<SampleData>(queryDefinition);
    var results = new List<SampleData>();
    while (queryResultSetIterator.HasMoreResults)
    {
        var currentResultSet = await queryResultSetIterator.ReadNextAsync();
        foreach (var result in currentResultSet)
            results.Add(result);
    }
    tickCount2 = Environment.TickCount - tickCount;
    WriteLine($"Found {results.Count} results in {tickCount} ms");
 }

Answer 1

Thank you Gaurav Mantri, David Makogon and Mark Brown. Posting your suggestions as answer to help other community members.

Practices that you can adopt to make the connection faster

1. Initialize the cosmos connection at startup. you would need to use CreateAndInitializeAsync method of the CosmosClient.
2. Make sure to run the code in the same region as that of cosmos DB.
3. Always have the reference to cosmos client and container alive. This will ensure the subsequent calls (after 1st call) will be faster.

Reference:

1. Why the first request takes so much time and how you can speed that up.
2. https://stackoverflow.com/questions/67943528/asp-net-core-3-application-slow-to-load-cosmos-db-query#:~:text=First%2C%20I%20would,from%2Dportal%22%2C%0AcontainersToInitialize)