ETag
An ETag is a version identifier on each Azure Cosmos DB item used to implement optimistic concurrency control. DP-420 uses it to prevent lost updates by rejecting a write if the item changed since it was read.
All DP-420 Terms
Azure Cosmos DB
Azure Cosmos DB is Microsoft's globally distributed, multi-model NoSQL database with single-digit-millisecond latency and elastic scale.
Partition Key
A Partition Key is the document property Azure Cosmos DB uses to distribute data across logical partitions for scale.
Logical Partition
A Logical Partition is the set of all items in a container that share the same partition key value, and it has a 20 GB storage limit.
Request Unit (RU)
A Request Unit (RU) is the normalized currency of throughput in Azure Cosmos DB, abstracting CPU, memory, and IOPS into one cost per operation.
Provisioned Throughput
Provisioned Throughput is the model where you reserve a fixed number of Request Units per second, as standard or autoscale, for a database or container.
Autoscale
Autoscale is a provisioned-throughput mode that automatically scales Request Units per second between 10% and 100% of a set maximum based on usage.
Consistency Level
A Consistency Level defines the trade-off between data freshness, availability, latency, and RU cost across replicas.
Multi-region Writes
Multi-region Writes let an Azure Cosmos DB account accept writes in more than one region, improving write availability and latency.
Conflict Resolution
Conflict Resolution is the policy that decides which write wins when multi-region writes produce competing updates, using last-writer-wins or a custom procedure.
Change Feed
The Change Feed is a persistent, ordered record of changes to items in a container that applications can process incrementally.
Analytical Store
The Analytical Store is a column-oriented copy of container data, automatically synced from the transactional store, for analytics without impacting operational workloads.
Time to Live (TTL)
Time to Live (TTL) is a setting that automatically deletes items after a specified period, configurable per container and per item.
ETag
An ETag is a version identifier on each Azure Cosmos DB item used to implement optimistic concurrency control.
Hierarchical Partition Key
A Hierarchical Partition Key (HPK) uses multiple levels of properties as the partition key so that a shared prefix can hold more than the 20 GB per single key value, while each full key path stays within the logical-partition limits.
Indexing Policy
An Indexing Policy defines which item paths Azure Cosmos DB indexes and how, controlling query performance and RU cost.