How do you read/write from Cosmos DB using bindings?

Short answer: Use [CosmosDBTrigger] for input and [CosmosDB] for output. Example (input Cosmos DB trigger): [FunctionName("CosmosDBTriggerFunction")] public static void Run( [CosmosDBTrigger( databaseName: "MyDatabase", collectionName: "MyCollection", ConnectionStringSetting = "CosmosDBConnection", LeaseCollectionName = "leases")] IReadOnlyList<Document> input, ILogger log) {

Example code

foreach (var doc in input)
{ log.LogInformation($"Document received: {doc.Id}"); }
} Example (output Cosmos DB binding): [CosmosDB( databaseName: "MyDatabase", collectionName: "MyCollection", ConnectionStringSetting = "CosmosDBConnection")] out dynamic outputDoc outputDoc = new { id = Guid.NewGuid(), Name = "New Item" };

Real-world example (ShopNest)

ShopNest on Azure typically uses App Service + SQL Database + Blob Storage + Application Insights for monitoring.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.