Design a car rental platform focusing on core entities, relational database schema, and API interfaces. Define key entities and relationships (e.g., customer, vehicle, vehicle_type, branch/location, inventory/unit, reservation, rental/contract, payment, pricing rule, promotion, insurance, availability/hold, staff, damage report). Propose table definitions with primary/foreign keys, unique constraints, and essential indexes (e.g., availability lookups by location and date). Describe workflows and consistency requirements for: search availability by location and date/time windows; create/modify/cancel reservation with holds to prevent double-booking; pick-up (vehicle assignment, contracts, inspection) and return (mileage, fuel, damage, late fees); pricing (base rate, mileage, insurance add-ons, taxes, promotions); payments (authorization, capture, refunds). Provide 3–5 representative REST endpoints with request/response fields (e.g., POST /search, POST /reservations, PATCH /reservations/{id}, POST /rentals/{id}/return). Discuss idempotency, pagination, authentication/authorization, concurrency control (row locks or optimistic versioning), and a plan to scale (read replicas, partitioning by branch/region, caching hot availability queries).

This question evaluates data modeling, transactional integrity, concurrency control, REST API and workflow design, and system scalability within the car rental domain in the System Design category.

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Design car rental schema and APIs | Retool Interview Question

System Design: Car Rental Platform

Objective

Design a car rental platform with:

Core entities and relationships (customer, vehicle, vehicle_type, branch/location, inventory/unit, reservation, rental/contract, payment, pricing rule, promotion, insurance, availability/hold, staff, damage report).
A relational database schema with primary/foreign keys, unique constraints, and essential indexes (e.g., availability lookups by location and date/time windows).
End-to-end workflows and consistency requirements for:
1. Searching availability by location and date/time window.
2. Creating, modifying, and canceling reservations with holds to prevent double-booking.
3. Pick-up (vehicle assignment, contracts, inspection) and return (mileage, fuel, damage, late fees).
4. Pricing (base rate, mileage, insurance add-ons, taxes, promotions).
5. Payments (authorization, capture, refunds).
3–5 representative REST endpoints with request/response fields (e.g., POST /search, POST /reservations, PATCH /reservations/{id}, POST /rentals/{id}/return).
Cross-cutting concerns: idempotency, pagination, authentication/authorization, concurrency control (row locks or optimistic versioning), and scaling (read replicas, partitioning by branch/region, caching hot availability queries).

Constraints and Assumptions

Use a relational database (e.g., PostgreSQL). Time stored in UTC; branch has local timezone metadata.
Availability is primarily per vehicle type at a branch; specific unit assignment occurs at pickup.
Overlaps and double-booking are prevented via transactional holds and constraints.

Objective

Design a car rental platform with:

Core entities and relationships (customer, vehicle, vehicle_type, branch/location, inventory/unit, reservation, rental/contract, payment, pricing rule, promotion, insurance, availability/hold, staff, damage report).

A relational database schema with primary/foreign keys, unique constraints, and essential indexes (e.g., availability lookups by location and date/time windows).

End-to-end workflows and consistency requirements for:

Searching availability by location and date/time window.
Creating, modifying, and canceling reservations with holds to prevent double-booking.
Pick-up (vehicle assignment, contracts, inspection) and return (mileage, fuel, damage, late fees).
Pricing (base rate, mileage, insurance add-ons, taxes, promotions).
Payments (authorization, capture, refunds).

3–5 representative REST endpoints with request/response fields (e.g., POST /search, POST /reservations, PATCH /reservations/{id}, POST /rentals/{id}/return).

Cross-cutting concerns: idempotency, pagination, authentication/authorization, concurrency control (row locks or optimistic versioning), and scaling (read replicas, partitioning by branch/region, caching hot availability queries).

Design car rental schema and APIs

Quick Overview

System Design: Car Rental Platform

Objective

Constraints and Assumptions

Solution

Submit Your Answer to Earn 20XP

Design car rental schema and APIs

Quick Overview

System Design: Car Rental Platform

Objective

Constraints and Assumptions

Solution

Submit Your Answer to Earn 20XP