Document versioning in Elasticsearch - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the version number after the update?

Given a document indexed with version 3, what will be the version number after a successful update using optimistic concurrency control with version 3?

Elasticsearch

PUT /my_index/_doc/1?version=3
{
  "field": "new value"
}

A 4

B 3

C 5

D Version conflict error

💡 Hint

When you update a document with the correct version, Elasticsearch increments the version.

Elasticsearch uses optimistic concurrency control. If you specify the current version (3) when updating, the update succeeds and the version increments to 4.

❓ Predict Output

intermediate

What happens if you update with an outdated version?

If a document currently has version 5, what happens when you try to update it specifying version 3?

Elasticsearch

PUT /my_index/_doc/1?version=3
{
  "field": "another value"
}

A Update succeeds and version becomes 6

B Update succeeds but version stays 5

C Elasticsearch ignores the version and updates anyway

D Update fails with a version conflict error

💡 Hint

Elasticsearch prevents updates if the version does not match the current document version.

When you specify a version lower than the current document version, Elasticsearch rejects the update with a version conflict error to avoid overwriting newer data.

🧠 Conceptual

advanced

How does Elasticsearch handle versioning with external versioning?

Which statement best describes how external versioning works in Elasticsearch?

A Elasticsearch automatically sets the version based on the timestamp of the update

B Elasticsearch ignores the version and always increments internally

C You provide the version number and Elasticsearch only updates if the provided version is higher than the current

D External versioning disables version checks and always overwrites the document

💡 Hint

External versioning lets you control the version number yourself.

With external versioning, you supply the version number. Elasticsearch updates the document only if the provided version is greater than the current version, ensuring your external system controls version order.

❓ Predict Output

advanced

What is the output of this version conflict scenario?

Consider this sequence: 1. Document version is 2. 2. Two concurrent updates try to update with version 2. What happens to the second update?

Elasticsearch

PUT /my_index/_doc/1?version=2
{
  "field": "update A"
}

PUT /my_index/_doc/1?version=2
{
  "field": "update B"
}

A Second update overwrites first without error

B First update succeeds, second update fails with version conflict

C Both updates fail with version conflict

D Both updates succeed and version becomes 4

💡 Hint

Only one update can succeed with the same version number.

The first update with version 2 succeeds and increments the version to 3. The second update still uses version 2, which is now outdated, so it fails with a version conflict error.

🧠 Conceptual

expert

Why is versioning important in Elasticsearch document updates?

Select the best reason why Elasticsearch uses versioning for documents.

A To prevent lost updates by ensuring only the latest changes overwrite older ones

B To allow multiple users to edit the same document simultaneously without conflicts

C To track the number of times a document has been read

D To automatically backup documents after each update

💡 Hint

Think about what happens if two updates happen at the same time.

Versioning helps Elasticsearch avoid lost updates by making sure that only updates with the correct or newer version overwrite the document, preventing older data from overwriting newer changes.