Shard key selection in HLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to select the shard key based on user ID.

HLD

shard_key = [1]

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

Asession_id

Btimestamp

Cuser_id

Drequest_type

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a non-unique or rapidly changing attribute like timestamp.

Using request_type which may not distribute data evenly.

The shard key should be a stable and evenly distributed attribute like user_id to ensure balanced data distribution.

2fill in blank

medium

Complete the code to ensure shard key supports range queries.

HLD

if shard_key == [1]:
    enable_range_queries = True

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

Arequest_type

Buser_id

Csession_id

Dtimestamp

Attempts:

3 left

💡 Hint

Common Mistakes

Using user_id which is not ordered.

Choosing session_id which may not be sequential.

timestamp is suitable for range queries because it represents a continuous timeline.

3fill in blank

hard

Fix the error in shard key selection to avoid hotspotting.

HLD

shard_key = [1]  # Avoid using this key to prevent hotspots

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

Afixed_value

Btimestamp

Cregion_code

Duser_id

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing fixed_value which leads to all data in one shard.

Using region_code which might cause uneven distribution if skewed.

Using a fixed_value as shard key causes all data to go to one shard, creating a hotspot.

4fill in blank

hard

Fill both blanks to create a shard key that balances distribution and supports queries.

HLD

shard_key = ([1], [2])  # Composite shard key

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

Auser_id

Btimestamp

Cregion_code

Dsession_id

Attempts:

3 left

💡 Hint

Common Mistakes

Using two non-unique or non-distributed keys.

Choosing keys that do not support query patterns.

Combining user_id and timestamp helps balance data and supports range queries.

5fill in blank

hard

Fill all three blanks to define shard key selection logic with validation.

HLD

def select_shard_key(record):
    key = record.get([1])
    if key is None or not isinstance(key, [2]):
        raise ValueError('Invalid shard key')
    return key if key [3] 0 else None

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

A'user_id'

Bint

C>

Dstr

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong key name or type.

Missing validation for key presence or type.

Using incorrect comparison operator.

The function gets 'user_id' from the record, checks it is an int, and ensures it is positive with > 0.