Q1. What is caching and why is it used?
Caching stores a copy of data in a faster or closer tier so future reads avoid the slower origin. It reduces latency, increases throughput, lowers load and cost on databa...
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Q2. What are Core Web Vitals and what thresholds define a good experience?
Core Web Vitals are user-centric metrics for loading, interactivity and visual stability. LCP, Largest Contentful Paint, measures when the largest visible element, usuall...
Q3. How do you improve Largest Contentful Paint?
LCP is dominated by four factors: time to first byte, resource load time, render-blocking resources and client-side rendering delay. First ensure fast TTFB with caching, ...
Q4. When should you use StringBuilder instead of string concatenation?
`string` is immutable: every operation such as concatenation or `Replace` allocates a new string. `StringBuilder` is a mutable buffer backed by a resizable array, so appe...
Q5. Compare ArrayList, LinkedList and HashMap.
- ArrayList: array-backed, O(1) random access, amortised O(1) append, O(n) insertion/removal in the middle. Best default for ordered lists. - LinkedList: doubly linked, O...
Q6. How do indexes work in MongoDB and what is a compound index?
An index is a B-tree structure storing a sorted subset of a collection's fields, letting the planner find documents without scanning everything. Without an index a query ...
Q7. What causes Cumulative Layout Shift and how do you fix it?
CLS measures how much visible content moves unexpectedly. The score for a shift is the impact fraction times the distance fraction, summed over the session, excluding shi...
Q8. Explain caching strategies and common failure modes.
Strategies: - Cache-aside (lazy loading): app checks cache, on miss reads DB and populates. Most common. - Read-through: cache library fetches on miss. - Write-through: w...
Q9. How do you scale a Node.js application across CPU cores?
Node runs JavaScript on a single thread, so scaling options are: - Cluster module or a process manager (PM2) to fork one process per core behind a shared port. Good for t...
Q10. What is the difference between a clustered and a non-clustered index?
A clustered index defines the physical order of rows in the table. Because the data is stored in that order, a table can have only one clustered index, usually the primar...