Design a unique ID generator in HLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to choose the component responsible for generating unique IDs.

HLD

The unique ID generator system primarily uses a [1] to create IDs.

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

Atimestamp

Bload balancer

Ccache

Ddatabase

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing database as the primary generator instead of timestamp.

Confusing cache with ID generation.

The timestamp is commonly used to ensure uniqueness by incorporating the current time into the ID.

2fill in blank

medium

Complete the code to select the method that prevents ID collisions in a distributed system.

HLD

To avoid ID collisions, the system uses [1] to differentiate IDs generated by different nodes.

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

Arandom numbers

Bencryption

Cnode identifiers

Dcaching

Attempts:

3 left

💡 Hint

Common Mistakes

Using random numbers alone which can cause collisions.

Thinking encryption prevents collisions.

Node identifiers help ensure that IDs generated on different machines do not clash.

3fill in blank

hard

Fix the error in the ID generation logic to ensure IDs are sortable by creation time.

HLD

ID = [1] + node_id + sequence_number

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

AUUID

Brandom_number

Chash_value

Dtimestamp

Attempts:

3 left

💡 Hint

Common Mistakes

Using random_number which does not guarantee order.

Using UUID which is not time sortable.

Using a timestamp at the start ensures IDs can be sorted by creation time.

4fill in blank

hard

Fill both blanks to complete the ID structure with time and uniqueness components.

HLD

ID = [1] + [2]

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

Atimestamp

Bnode_id

Crandom_suffix

Dchecksum

Attempts:

3 left

💡 Hint

Common Mistakes

Using random_suffix instead of node_id which can cause collisions.

Adding checksum which is not necessary for uniqueness.

The ID combines a timestamp and a node identifier to ensure uniqueness and order.

5fill in blank

hard

Fill all three blanks to complete the ID generation formula ensuring uniqueness, order, and scalability.

HLD

ID = [1] + [2] + [3]

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

Atimestamp

Bsequence_number

Cnode_id

Drandom_number

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up sequence_number and node_id positions.

Using random_number which can cause collisions.

The ID uses a timestamp for order, a node ID for source uniqueness, and a sequence number to handle multiple IDs generated in the same timestamp.

Practice

1. What is the primary purpose of a unique ID generator in a distributed system?

easy

A. To create identifiers that are distinct across all machines and time

B. To encrypt data for secure communication

C. To compress large files efficiently

D. To balance load between servers

Solution

1. Step 1: Understand the role of unique IDs

   Unique IDs ensure that each identifier is different from others, avoiding conflicts.

2. Step 2: Recognize distributed system needs

   In distributed systems, IDs must be unique across machines and time to prevent collisions.

3. Final Answer:

   To create identifiers that are distinct across all machines and time -> Option A

4. Quick Check:

   Unique ID purpose = distinct identifiers [OK]

Hint: Unique IDs prevent duplicates across systems [OK]

Common Mistakes:

• Confusing unique ID with encryption
• Thinking unique ID compresses data
• Mixing load balancing with ID generation

2. Which of the following is a common component in a unique ID generator design?

easy

A. Encryption key for data security

B. Load balancer to distribute requests

C. Compression algorithm for data size reduction

D. Sequence number to avoid collisions within the same timestamp

Solution

1. Step 1: Identify components of unique ID generators

   Common components include timestamp, machine identifier, and sequence number.

2. Step 2: Understand sequence number role

   Sequence numbers help generate multiple unique IDs within the same timestamp to avoid collisions.

3. Final Answer:

   Sequence number to avoid collisions within the same timestamp -> Option D

4. Quick Check:

   Sequence number = collision avoidance [OK]

Hint: Sequence numbers prevent same-time ID clashes [OK]

Common Mistakes:

• Confusing encryption with ID generation
• Thinking compression is part of ID design
• Mixing load balancing with ID components

3. Consider a unique ID generator that uses a 41-bit timestamp, 10-bit machine ID, and 12-bit sequence number. What is the maximum number of unique IDs it can generate per millisecond per machine?

medium

A. 8192

B. 1024

C. 4096

D. 2048

Solution

1. Step 1: Understand bit allocation for sequence number

   The sequence number uses 12 bits, so max IDs per millisecond = 2^12.

2. Step 2: Calculate 2^12

   2^12 = 4096 unique IDs per millisecond per machine.

3. Final Answer:

   4096 -> Option C

4. Quick Check:

   2^12 = 4096 [OK]

Hint: 2^sequence_bits = max IDs/ms [OK]

Common Mistakes:

• Using machine ID bits instead of sequence bits
• Calculating 2^10 or 2^11 instead of 2^12
• Confusing total bits with sequence bits

4. A unique ID generator uses a timestamp, machine ID, and sequence number. If two machines generate IDs at the exact same millisecond with the same sequence number, what is the likely cause of duplicate IDs?

medium

A. Machine IDs are not unique or not included in the ID

B. Timestamp is too large

C. Sequence number is too long

D. The system uses encryption

Solution

1. Step 1: Analyze ID components for uniqueness

   Machine ID differentiates IDs from different machines at the same time.

2. Step 2: Identify cause of duplicates

   If machine IDs are missing or not unique, IDs from different machines can collide.

3. Final Answer:

   Machine IDs are not unique or not included in the ID -> Option A

4. Quick Check:

   Missing unique machine ID = duplicates [OK]

Hint: Unique machine ID prevents cross-machine duplicates [OK]

Common Mistakes:

• Blaming timestamp size for duplicates
• Thinking longer sequence number causes duplicates
• Confusing encryption with ID uniqueness

5. You need to design a unique ID generator for a global system with thousands of machines generating millions of IDs per second. Which design choice best ensures scalability and uniqueness?

hard

A. Generate random 64-bit numbers without coordination

B. Use a 64-bit ID combining timestamp, machine ID, and sequence number with synchronized clocks

C. Use only timestamp-based IDs without machine info

D. Assign IDs sequentially from a central server

Solution

1. Step 1: Consider scalability and uniqueness needs

   Global scale requires IDs unique across machines and time, with high throughput.

2. Step 2: Evaluate design options

   Combining timestamp, machine ID, and sequence number in 64 bits with synchronized clocks ensures uniqueness and scalability.

3. Step 3: Reject other options

   Random IDs risk collisions; timestamp-only lacks machine uniqueness; central server causes bottleneck.

4. Final Answer:

   Use a 64-bit ID combining timestamp, machine ID, and sequence number with synchronized clocks -> Option B

5. Quick Check:

   64-bit composite ID = scalable unique IDs [OK]

Hint: Combine time, machine, sequence for scalable unique IDs [OK]

Common Mistakes:

• Relying on random IDs risking collisions
• Ignoring machine ID causing duplicates
• Using central server causing bottlenecks