Azure Cosmos DB

Consistency impacts latency and throughput. Use Session for most real‑time scenarios, and Strong only when absolute consistency is required.

// Example: Set session consistency in .NET SDK
var client = new CosmosClient(connectionString,
    new CosmosClientOptions{ ConsistencyLevel = ConsistencyLevel.Session });

Select a partition key that provides high cardinality and even distribution. Avoid hot partitions.

• Prefer fields that are frequently used in queries.
• Ensure the key value space is large.

// Example: Defining a container with a partition key
await database.CreateContainerIfNotExistsAsync(
    new ContainerProperties("Orders", "/customerId"));

Exclude rarely queried fields to reduce index write costs.

{
  "indexingMode": "consistent",
  "includedPaths": [{ "path": "/*" }],
  "excludedPaths": [{ "path": "/metadata/?" }]
}

Bulk mode improves throughput when inserting or updating large batches.

// .NET bulk insert example
var bulkOperations = items.Select(item => 
    new TransactionalBatchItem(item));
await container.ExecuteTransactionalBatchAsync(bulkOperations);

Process inserts/updates efficiently without polling.

// Sample Change Feed processor (Node.js)
const { ChangeFeedProcessor } = require("@azure/cosmos");
await processor.start();

Autoscale adapts RU/s based on traffic, preventing throttling.

// Enable autoscale at container creation
await database.CreateContainerIfNotExistsAsync(
    new ContainerProperties("Events", "/eventType"),
    throughput: 4000, // Max RU/s
    autoscaleSettings: new AutoscaleSettings { MaxThroughput = 10000 });

Enable request logging to identify latency hotspots.

// Enable diagnostics in Java SDK
CosmosClientBuilder clientBuilder = new CosmosClientBuilder(connectionString)
    .gatewayMode()
    .contentResponseOnWriteEnabled(true)
    .diagnosticThresholds(new CosmosDiagnosticsThresholds()
        .setPointOperationLatencyThreshold(Duration.ofMillis(200)));