Firestore queries and indexes in GCP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a Firestore index and why is it important?

A Firestore index is a data structure that helps Firestore quickly find and sort documents based on query conditions. It is important because without proper indexes, queries can be slow or fail to run.

intermediate

What types of queries require composite indexes in Firestore?

Queries that filter or sort on multiple fields at the same time require composite indexes. For example, querying where 'status' is 'active' and ordering by 'createdDate' needs a composite index.

beginner

How does Firestore handle queries without an existing index?

Firestore returns an error with a direct link to create the required index in the Firebase console. This helps you quickly add the needed index for your query to work.

intermediate

What is the difference between single-field and composite indexes in Firestore?

Single-field indexes are automatically created for each field and support simple queries. Composite indexes combine multiple fields and support complex queries with multiple filters or sort orders.

advanced

Why should you avoid unnecessary indexes in Firestore?

Unnecessary indexes increase storage costs and slow down write operations because Firestore updates all relevant indexes when data changes. Keeping only needed indexes improves performance and reduces cost.

Which Firestore query requires a composite index?

A Query filtering by one field only

B Query ordering by a single field

C Query filtering by two fields and ordering by one

D Query fetching all documents without filters

Queries that filter or order by multiple fields need composite indexes.

What happens if you run a Firestore query without the needed index?

A The query returns an error with a link to create the index

B Firestore ignores the missing index and returns partial results

C The query runs slowly but returns results

D Firestore automatically creates the index

Firestore returns an error and provides a link to create the missing index.

Which index type is created automatically for each field in Firestore?

A Composite index

B No index is created automatically

C Full-text index

D Single-field index

Single-field indexes are created automatically for each field.

Why should you limit the number of indexes in Firestore?

A Indexes increase storage costs and slow writes

B Indexes slow down read operations

C Indexes cause data loss

D Indexes prevent queries from running

More indexes mean higher storage costs and slower write performance.

Which Firestore query can run without any composite index?

A Query filtering by two fields

B Query filtering by one field only

C Query ordering by two fields

D Query filtering and ordering by multiple fields

Queries filtering or ordering by a single field use single-field indexes.

Explain how Firestore uses indexes to speed up queries and what happens if an index is missing.

Think about how a book index helps you find pages fast.

Describe best practices for managing Firestore indexes to balance performance and cost.

Less clutter means faster work and lower bills.