Design 64-bit distributed IDs and a parking lot
Company: Flipster
Role: Software Engineer
Category: System Design
Difficulty: easy
Interview Round: Technical Screen
You have two system-design prompts.
## 1) 64-bit database ID generator
Design a service/library that generates **globally unique 64-bit integer IDs** for database records in a **distributed system**.
### Requirements
- IDs must be **unique across all shards/regions**.
- Very high write rate (assume **100K–1M IDs/sec** globally).
- Prefer IDs that are **roughly time-ordered** to reduce index fragmentation.
- Support **sharding** and growth in number of nodes.
- Discuss how to **avoid conflicts** and what happens on failures (node restart, clock issues, network partitions).
### Deliverables
- Bit layout proposal (what each bit range means).
- How nodes obtain any needed configuration (e.g., worker IDs).
- How the system behaves under clock skew/rollback.
- Operational considerations (monitoring, rotation, migrations).
## 2) Parking lot system (object-oriented + backend)
Design a parking lot management system.
### Requirements (assume typical)
- Multiple levels; each level has multiple spots of different types (compact/large/EV/handicapped).
- Vehicles arrive/leave; system issues a ticket and calculates fees.
- Track spot availability and prevent double-allocation under concurrency.
- Provide APIs for: entering, exiting, querying availability, and (optionally) reserving a spot.
### Deliverables
- Core classes/entities and relationships.
- Key APIs and data storage approach.
- Concurrency/consistency approach for assigning/freeing spots.
Overview: The question evaluates distributed-systems and scalability competencies for globally unique 64-bit ID generation (including sharding, time-ordering, fault tolerance and clock issues) as well as object-oriented design, concurrency control, API design, and data modeling for a parking lot backend.