Concurrency control

As explained in Microsoft Azure in Action

Concurrency control is the management of simultaneous operations so that shared data remains consistent according to the system's rules.

Concurrency control keeps simultaneous operations from corrupting shared data. In Azure Cosmos DB, optimistic concurrency lets operations proceed without locking, then checks for conflicts before accepting an update. section 11.4.3

Cosmos DB uses a version-checking workflow:

• A read stores the document’s ETag, which represents its current version. section 11.4.3
• An update includes that ETag and succeeds only if the document has not changed since it was read. section 11.4.3
• If another operation changed the document, the ETag no longer matches and the update fails instead of overwriting newer data. section 11.4.3
• The application can retry the read-update cycle using the latest document version. section 11.4.3

Updating inventory during a busy sale

Suppose two shoppers trigger inventory updates for the same product. Each operation reads the product and its ETag. The first update changes the document and its ETag; the second update detects the mismatch, fails safely, and can reread the inventory before retrying. section 11.4.3

Figure 11.7 A read operation stores the ETag value for concurrency in future updates.

A read operation stores the ETag for use in a later conditional update. section 11.4.3

How Microsoft Azure in Action covers it

How deep it goes

Explains optimistic concurrency, ETag checks, conflict failure, and read-update retries without detailing transaction internals.

Examples

Uses concurrent product-inventory updates and a read operation that stores an ETag for a later update.

What it assumes

Assumes Azure Cosmos DB documents and simultaneous operations; teaches ETags and optimistic conflict handling directly.

What you can do after

Diagnose/debug with it: detect stale updates through ETag mismatches and retry the read-update cycle safely.

How it connects

Connects optimistic concurrency with ETags, transactions, data consistency, and Azure Cosmos DB documents.

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Related concepts

• optimistic lockingincludes · A concurrency-control technique that detects conflicting updates by validating a version or equivalent state when changes are applied, rather than preventing concurrent access in advance.
• Hibernateused by · Hibernate is a Java object-relational mapping and persistence framework that maps application objects to relational database data.
• lockingincludes · Locking is a synchronization technique that restricts concurrent access to shared resources or protected operations.
• databasepart of · A database is an organized collection of persistent data managed by software for storage, retrieval, querying, and modification.
• optimistic concurrency controlincludes · Optimistic concurrency control is a concurrency-control technique that allows operations to proceed with limited locking and detects conflicting changes through validation before committing updates.

This explainer was generated by Manning's knowledge graph from the text of Microsoft Azure in Action. The section links point to the parts of the book it draws on.