Document ID strategies (auto vs manual) in Elasticsearch - Practice Questions

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Elasticsearch indexing operation with manual ID?

Consider this Elasticsearch indexing request using a manual document ID:

{
  "index": "products",
  "id": "12345",
  "body": {
    "name": "Laptop",
    "price": 1200
  }
}

What will be the result if you try to index the same document with the same ID again but with a different price?

Elasticsearch

POST /products/_doc/12345
{
  "name": "Laptop",
  "price": 1300
}

A The document with ID '12345' will be updated with the new price 1300.

B Elasticsearch will create a new document with a different ID automatically.

C An error will occur because the ID '12345' already exists.

D The original document will remain unchanged and the new document will be rejected silently.

💡 Hint

Think about how Elasticsearch handles indexing with the same manual ID.

When you index a document with a manual ID that already exists, Elasticsearch updates the existing document with the new content.

❓ Predict Output

intermediate

What happens when you index documents without specifying an ID?

Given this indexing request without specifying an ID:

POST /orders/_doc
{
  "order_id": "A001",
  "amount": 250
}

What will Elasticsearch do?

Elasticsearch

POST /orders/_doc
{
  "order_id": "A001",
  "amount": 250
}

A The document will be rejected because ID is missing.

B The document will be indexed with 'order_id' as the ID automatically.

C An error will occur because the ID field is required in the body.

D Elasticsearch will generate a unique ID automatically for the document.

💡 Hint

Think about the default behavior when no ID is provided.

When no ID is specified, Elasticsearch generates a unique ID automatically for each document.

🧠 Conceptual

advanced

Which is a key advantage of using manual document IDs in Elasticsearch?

Choose the main advantage of assigning manual IDs to documents instead of letting Elasticsearch generate them automatically.

A It improves Elasticsearch's internal indexing speed significantly.

B It allows easy updates and overwrites of documents by referencing the same ID.

C It guarantees that documents will never be deleted accidentally.

D It automatically prevents duplicate documents with the same content.

💡 Hint

Think about how manual IDs help with document management.

Manual IDs let you update or overwrite documents easily by using the same ID to reference them.

❓ Predict Output

advanced

What error occurs when indexing with an invalid ID format?

Consider this indexing request with an invalid ID containing spaces:

POST /users/_doc/invalid%20id
{
  "name": "Alice"
}

What error will Elasticsearch return?

Elasticsearch

POST /users/_doc/invalid%20id
{
  "name": "Alice"
}

A 500 Internal Server Error due to server crash.

B Document indexed successfully with ID 'invalid id'.

C 400 Bad Request with error about invalid ID format.

D 404 Not Found because the index does not exist.

💡 Hint

Think about allowed characters in Elasticsearch document IDs.

Elasticsearch IDs cannot contain spaces; it returns a 400 error for invalid ID format.

🧠 Conceptual

expert

Why might auto-generated IDs cause performance issues in Elasticsearch?

Choose the best explanation why using auto-generated document IDs can sometimes reduce indexing performance.

A Because auto-generated IDs are random, they cause frequent shard relocations and reduce cache efficiency.

B Because auto-generated IDs are sequential, they cause index fragmentation.

C Because auto-generated IDs prevent Elasticsearch from compressing stored data.

D Because auto-generated IDs require manual conflict resolution by the user.

💡 Hint

Think about how random IDs affect data distribution in shards.

Random auto-generated IDs cause documents to be spread across shards unpredictably, leading to more shard relocations and less efficient caching.