Querying & Indexing in Azure Cosmos DB: Complete Guide | James Codella | Azure Cosmos DB Conf 2026
James Codella explains how Azure Cosmos DB query performance and cost come down to two core tasks: routing a query to the right partitions and efficiently finding the right documents inside those partitions. The session breaks down how the query engine and indexing system work together, with demos showing RU differences between indexed and non-indexed queries.
Full summary based on transcript
Query fundamentals: routing + indexing
- Every query must:
- Route to the correct partition(s)
- Identify matching documents within those partitions
- Key areas covered:
- Partition routing behavior
- How indexing affects query execution
- How to read query metrics to understand RU consumption and performance
Cosmos DB SQL query language features
- SQL query language capabilities discussed include:
- Joins
- Aggregates
- Subqueries
- System functions
Index types available in Azure Cosmos DB
- Index types covered:
- Range indexes
- Composite indexes
- Geospatial indexes
- Full text indexes
- Vector indexes
Index management and operational considerations
- Indexing topics covered:
- Indexing policies
- Index builds
- Rebuild considerations and trade-offs
Advanced optimization techniques
- Optimization topics covered:
- Computed properties
- Identifying and troubleshooting high-RU queries
- Demos emphasize that small indexing changes can significantly reduce RU cost.
Event and related links
- Cosmos Conf 2026 playlist: https://aka.ms/CosmosConf26Playlist
- Cosmos Conf Challenge (DP-420 voucher for first 500 completions): https://aka.ms/CosmosDBConfChallenge
- Post-event survey: https://aka.ms/CosmosConf2026Survey
- Conference site: https://aka.ms/azurecosmosdbconf
Speaker
- James Codella (Principal PM, Azure Cosmos DB)