Low-level design diagram of a parking lot system showing floors, spots, vehicles, and ticket flow

Parking Lot LLD — What I Learned Building It

Parking Lot LLD — What I Learned Building It I recently started practicing Low Level Design problems to strengthen my system design and backend thinking. The second problem I picked was the classic Parking Lot System. At first, it looked simple. But while building it, I realized these problems are less about writing code and more about: Modeling real-world systems Managing state correctly Designing scalable abstractions Avoiding bad object-oriented practices Code Repo parking lot ...

May 10, 2026 · 4 min · 653 words · Hitesh Patel
Low-level design diagram of an elevator system using active and shadow queue strategy

Elevator System Design LLD - Active & Shadow Queue

In the Previous attempt we designed an elevator system using two queues — an up queue and a down queue. But that system had some problems. It changed direction abruptly and did not respect the order of requests. To overcome this, the system has been redesigned with an active and shadow queue strategy that better mirrors how a real elevator behaves. The Requirements The requirements remain the same as the original design: ...

April 24, 2026 · 9 min · 1810 words · Hitesh Patel
Low-level design diagram of a single elevator system with queue-based SCAN scheduling

Elevator System Design (LLD): Single Lift Scheduling Explained

I have started learning low level system design and elevator is the first problem i picked up. In this i have picked the single elvator for simplicity and not get overwhelmed by it and get demotivated. So I built an elevator system. Lets improve this in stages. Not because it’s trendy. I have thought countless times standing in elevator does how it works. and after this i have my answer. ...

April 22, 2026 · 8 min · 1532 words · Hitesh Patel