Why Firestore performance needs planning in Firebase - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a Firestore query that limits results to 10 documents.

Firebase

const query = firestore.collection('users').limit([1]);

Drag options to blanks, or click blank then click option'

A'10'

B10

Climit

D100

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string instead of a number for limit

Using a method name instead of a number

The limit method expects a number to limit the number of documents returned. Using 10 returns only 10 documents.

2fill in blank

medium

Complete the code to order users by 'age' for efficient querying.

Firebase

firestore.collection('users').orderBy('[1]');

Drag options to blanks, or click blank then click option'

Aemail

Baddress

Cage

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Ordering by a field not indexed

Using a field unrelated to the query

Ordering by age requires an index for performance. Firestore uses indexes to speed up queries.

3fill in blank

hard

Fix the error in the Firestore query to avoid performance issues.

Firebase

firestore.collection('users').where('age', '[1]', 30);

Drag options to blanks, or click blank then click option'

A==

Bin

Carray-contains

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using unsupported operators without indexes

Using inequality operators that cause full scans

The == operator is used for equality checks and is efficient with indexes. Other operators may cause performance issues if not indexed properly.

4fill in blank

hard

Fill both blanks to create a query that filters users older than 25 and orders by age.

Firebase

firestore.collection('users').where('age', '[1]', 25).orderBy('[2]');

Drag options to blanks, or click blank then click option'

A>

B<

Cage

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong comparison operator

Ordering by a different field than filtered

Filtering with > 25 and ordering by age ensures efficient queries with proper indexing.

5fill in blank

hard

Fill all three blanks to create a performant Firestore query that filters by city, orders by last name, and limits results.

Firebase

firestore.collection('users').where('city', '==', '[1]').orderBy('[2]').limit([3]);

Drag options to blanks, or click blank then click option'

ANew York

BlastName

C10

DfirstName

Attempts:

3 left

💡 Hint

Common Mistakes

Using a non-indexed field for ordering

Not limiting query results

Filtering by city equals 'New York', ordering by lastName, and limiting to 10 documents improves query speed and reduces costs.