Back-End Development Back-End Performance and Caching 3

Question 1

What is profiling in back-end performance optimization?

Accepted Answer

Measuring the runtime behavior of code to identify bottlenecks in CPU usage, memory consumption, and execution time

Answer

Profiling tools instrument code to measure where time and resources are spent, revealing hot paths and bottlenecks that are the highest-value targets for optimization.

Question 2

What is the purpose of database read replicas in a high-traffic back-end system?

Accepted Answer

To offload read queries to replica servers, reducing load on the primary write database and improving read throughput

Answer

Read replicas receive a copy of all writes from the primary and serve SELECT queries, allowing read-heavy applications to scale horizontally without burdening the primary database.

Question 3

What is connection timeout and why should it be set in back-end applications?

Accepted Answer

The maximum time to wait for a database or external service connection before giving up and returning an error

Answer

Setting connection timeouts prevents threads from blocking indefinitely on unresponsive services, allowing the application to fail fast, release resources, and return a meaningful error to the client.

Question 4

What is a cold start in serverless back-end functions?

Accepted Answer

The latency incurred when a serverless function is invoked after being idle, requiring the provider to initialize the execution environment

Answer

Cold starts occur when a serverless function hasn't been invoked recently and the provider must spin up a new container instance, adding 100ms–3s of initialization latency to that first request.

Question 5

What does the term 'throughput' mean when measuring back-end performance?

Accepted Answer

The number of requests or transactions a system can process per unit of time

Answer

Throughput measures how many operations (requests, transactions, messages) a system handles per second or minute, indicating overall system capacity.

Back-End Development Practice Test

Back-End Development Practice Test

Back-End Development Back-End Performance and Caching 3