Design systems.
Write the code.
Prove it.
Structra is an online judge for Low-Level Design where your architecture is tested through real behavior, hidden tests, and evolving requirements — like LeetCode, but for the problems that decide system design interviews.
parking-lot/
go.mod
README.md
parking/
contract.go
system.go
types.go
func (s *system) Park(v Vehicle) (Ticket, error) { // your design…}The loop
A full engineering cycle, judged.
- 01
Understand
Read the problem statement, functional requirements, and the public contract you must satisfy.
- 02
Build
Design and implement a full repository — floors, spots, tickets — inside the workspace editor.
- 03
Submit
Send your entire project to the judge. Every file you wrote is compiled in a clean sandbox.
- 04
Get judged
Hidden tests verify behavior, static analysis scores your design. No reference architecture is imposed.
- 05
Evolve
Progress through pricing, extensibility and concurrency stages that change the requirements.
Built for real design work.
Your internal architecture is yours. Structra evaluates observable behavior and documented contracts — you are never required to reproduce a reference design.
Hidden tests
Your architecture is judged through observable behavior — never through a leaked test source.
Real projects
Submit a whole multi-file codebase, not a single function. Go and Java supported.
Heuristic design score
Static analysis gives a clearly-labeled design signal, kept separate from functional correctness.
Progressive stages
Base → Pricing → Extensibility → Concurrency. Each stage layers new requirements onto your design.
The judge is waiting.
Start with Parking Lot — a multi-floor system with pricing, electric vehicles and concurrency waiting in later stages.
Start Parking Lot