EasyFundamentals

Surge Pricing Driver Eligibility

Frequently Asked By:AppleGoogleAmazon

Interactive In-Browser Workspace

Practice this problem on live schema tables in PostgreSQL 16 WASM with instant row verification and visual EXPLAIN plans.

Solve in Workbench

Problem Statement

Find all qualifying drivers in `driver_profiles` who: - Are currently online (`is_online = true`) - Have vehicle tier in `'XL'` or `'Black'` - Have a driver `rating` of at least **4.85** - Have completed at least **100** `lifetime_trips` Return: 1. `driver_id` 2. `driver_name` 3. `vehicle_tier` 4. `rating` 5. `lifetime_trips` Order results by `rating` descending, then by `lifetime_trips` descending.

Why Technical Interviewers Ask This

During peak hours, QuickRide activates a 2.5x surge pricing multiplier. Only active online drivers in premium vehicle classes ('XL' and 'Black') who maintain a rating of 4.85 or higher and have at least 100 completed trips qualify for priority dispatch.

Common Pitfalls & Interview Traps

Forgetting required sorting and deterministic tie-breaking.

Not accounting for NULL or zero-value denominators during calculations.

Using inefficient quadratic subqueries instead of single-pass fundamentals constructs.

Canonical Modern SQL Solution

PostgreSQL 16 / ANSI SQL

SELECT 
        driver_id,
        driver_name,
        vehicle_tier,
        rating,
        lifetime_trips
      FROM driver_profiles
      WHERE is_online = true
        AND vehicle_tier IN ('XL', 'Black')
        AND rating >= 4.85
        AND lifetime_trips >= 100
      ORDER BY rating DESC, lifetime_trips DESC;

Approach Breakdown

This query addresses the problem requirements by filtering and structuring data in Fundamentals. It meets the target criteria: Online top-rated XL and Black tier drivers eligible for surge dispatch.

Edge Cases to Verbally Clarify with Your Interviewer

The dataset contains zero matching records (must return valid empty result without crashing).

Multiple records tie on sorting criteria (must evaluate tie-breaking order deterministically).

Foreign keys or secondary attributes have NULL values.

Frequently Asked Follow-Up Questions

What makes this question a favorite among Apple and Google interviewers?

Interviewers use this problem to test whether candidates write defensive, scalable Fundamentals queries that run efficiently on multi-million row production databases without excessive memory usage.

How does the query optimizer execute this query?

Using single-pass table scans with index lookups or sort buffers. Running EXPLAIN (ANALYZE, BUFFERS) in the DB Exercises workbench visualizes the execution nodes and buffer hit cache.