Throughput, latency, and availability in HLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define throughput as the number of requests processed per {{BLANK_1}}.

HLD

Throughput is measured as requests per [1].

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

Ahour

Bminute

Csecond

Dday

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a longer time unit like minute or hour, which is less precise for throughput.

Throughput is commonly measured as the number of requests processed per second to capture system performance.

2fill in blank

medium

Complete the code to define latency as the time taken to process a single {{BLANK_1}}.

HLD

Latency is the time taken to process a single [1].

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

Arequest

Bbatch

Cserver

Dconnection

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing latency with throughput or availability.

Latency measures the delay for processing one request from start to finish.

3fill in blank

hard

Fix the error in the availability formula by completing the code with the correct term for downtime: {{BLANK_1}}.

HLD

Availability = Uptime / (Uptime + [1])

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

Adowntime

Bthroughput

Cresponse_time

Dlatency

Attempts:

3 left

💡 Hint

Common Mistakes

Using response time or latency instead of downtime in the formula.

Availability is calculated as uptime divided by total time (uptime plus downtime).

4fill in blank

hard

Fill both blanks to complete the formula for average latency and throughput: average latency = total {{BLANK_1}} divided by total {{BLANK_2}}.

HLD

average_latency = total [1] / total [2]

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

Atime

Brequests

Cerrors

Dservers

Attempts:

3 left

💡 Hint

Common Mistakes

Using errors or servers instead of requests in the denominator.

Average latency is total time taken divided by total number of requests processed.

5fill in blank

hard

Fill all three blanks to complete the availability formula: availability = {{BLANK_1}} / ({{BLANK_2}} + {{BLANK_3}}).

HLD

availability = [1] / ([2] + [3])

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

Auptime

Bdowntime

Ctotal_time

Dresponse_time

Attempts:

3 left

💡 Hint

Common Mistakes

Using response time instead of total time or downtime.

Availability is uptime divided by total time, where total time is uptime plus downtime.

Practice

1. Which metric best describes how many requests a system can handle per second?

easy

A. Throughput

B. Latency

C. Availability

D. Scalability

Solution

1. Step 1: Understand throughput meaning

   Throughput measures the amount of work or requests a system can process in a given time.

2. Step 2: Compare with other metrics

   Latency measures response time, availability measures uptime, scalability is about growth capacity.

3. Final Answer:

   Throughput -> Option A

4. Quick Check:

   Throughput = Requests per second [OK]

Hint: Throughput = how much work done per time [OK]

Common Mistakes:

• Confusing latency with throughput
• Mixing availability with throughput
• Thinking scalability equals throughput

2. Which of the following correctly defines latency in system design?

easy

A. The total number of requests processed per second

B. The time taken to respond to a single request

C. The percentage of time the system is operational

D. The ability to add more servers to handle load

Solution

1. Step 1: Define latency

   Latency is the delay or time taken for a system to respond to one request.

2. Step 2: Eliminate other options

   The total number of requests processed per second describes throughput. The ability to add more servers to handle load describes scalability. The percentage of time the system is operational describes availability.

3. Final Answer:

   The time taken to respond to a single request -> Option B

4. Quick Check:

   Latency = Response time [OK]

Hint: Latency = response time per request [OK]

Common Mistakes:

• Confusing latency with throughput
• Thinking availability is latency
• Mixing scalability with latency

3. A system processes 1000 requests in 10 seconds. Each request takes 5 milliseconds to respond. What is the system's throughput and average latency?

medium

A. Throughput: 1000 requests/sec, Latency: 5 ms

B. Throughput: 100 requests/sec, Latency: 50 ms

C. Throughput: 10 requests/sec, Latency: 5 ms

D. Throughput: 100 requests/sec, Latency: 5 ms

Solution

1. Step 1: Calculate throughput

   Throughput = total requests / total time = 1000 / 10 = 100 requests per second.

2. Step 2: Understand latency

   Latency is given as 5 milliseconds per request.

3. Final Answer:

   Throughput: 100 requests/sec, Latency: 5 ms -> Option D

4. Quick Check:

   Throughput = 100, Latency = 5 ms [OK]

Hint: Throughput = total requests ÷ time; latency given directly [OK]

Common Mistakes:

• Dividing latency by number of requests
• Confusing throughput units
• Multiplying latency by total requests

4. A system claims 99.9% availability but is down for 10 minutes in a day. What is the actual availability and is the claim correct?

medium

A. Actual availability is 99.31%, claim is incorrect

B. Actual availability is 99.93%, claim is correct

C. Actual availability is 99.93%, claim is incorrect

D. Actual availability is 99.31%, claim is correct

Solution

1. Step 1: Calculate total minutes in a day

   24 hours x 60 minutes = 1440 minutes per day.

2. Step 2: Calculate availability

   Availability = (Total time - downtime) / Total time = (1440 - 10) / 1440 = 1430 / 1440 ≈ 0.9931 or 99.31%.

3. Step 3: Compare with claim

   Claim is 99.9%, actual is 99.31%, so claim is incorrect.

4. Final Answer:

   Actual availability is 99.31%, claim is incorrect -> Option A

5. Quick Check:

   Availability = 99.31%, Claim wrong [OK]

Hint: Availability = (uptime ÷ total time) x 100% [OK]

Common Mistakes:

• Using hours instead of minutes
• Incorrectly subtracting downtime
• Misreading percentage claim

5. You design a web service that must handle 10,000 requests per second with an average latency under 100 ms and 99.99% availability. Which design choice best balances these requirements?

hard

A. Use a single powerful server with caching to reduce latency

B. Use a database with strong consistency but no replication

C. Distribute load across multiple servers with load balancers and health checks

D. Optimize only latency by increasing CPU speed on one server

Solution

1. Step 1: Analyze throughput and availability needs

   10,000 requests/sec and 99.99% availability require scaling and fault tolerance.

2. Step 2: Evaluate design options

   Using a single powerful server with caching or optimizing CPU speed on one server risks overload and downtime. Using a database with strong consistency but no replication risks availability due to lack of fault tolerance. Distributing load across multiple servers with load balancers and health checks supports scaling and high availability.

3. Final Answer:

   Distribute load across multiple servers with load balancers and health checks -> Option C

4. Quick Check:

   Scaling + availability = load balancer + health checks [OK]

Hint: Scale horizontally with load balancers for throughput and availability [OK]

Common Mistakes:

• Relying on single server for high throughput
• Ignoring replication for availability
• Focusing only on latency without scaling