Full-Stack Development Case Studies & Practical Application 2

Question 1

A social media app experiences slow feed loading because each post requires a separate database call to fetch author details. Which pattern best resolves this N+1 query problem?

Accepted Answer

Use eager loading with a JOIN to fetch posts and authors in one query

Answer

Eager loading with a JOIN retrieves all required data in a single query, eliminating the N+1 problem.

Question 2

An e-commerce checkout page must never show a stale cart total, but product listing pages can tolerate slightly outdated prices. Which caching strategy fits this requirement?

Accepted Answer

Cache product listings with a short TTL; never cache the checkout total

Answer

Applying different caching policies per page type balances performance with data accuracy where it matters most.

Question 3

A startup's monolithic Node.js app is bottlenecked at its image-resize feature during peak hours. What is the most targeted fix without a full rewrite?

Accepted Answer

Extract image resizing into a separate microservice or worker queue

Answer

Extracting the bottleneck into an independent worker allows it to scale independently without disrupting the rest of the monolith.

Question 4

A React SPA communicates with a REST API. After a deploy, some users still see the old UI because the browser cached stale JS bundles. What build-time strategy prevents this?

Accepted Answer

Include a content hash in each bundle filename so new files bypass old cache entries

Answer

Content-hashed filenames ensure browsers treat new bundles as distinct resources and never serve stale files.

Question 5

A PostgreSQL-backed API endpoint is timing out under load. EXPLAIN ANALYZE shows a sequential scan on a 10M-row table. What is the immediate corrective action?

Accepted Answer

Add an index on the column used in the WHERE clause

Answer

Adding an index on the filtered column allows the query planner to perform an index scan instead of a sequential scan.

Full-Stack Development Practice Test

Full-Stack Development Practice Test

Full-Stack Development Case Studies & Practical Application 2