You’ve done LeetCode. Real interviews still break you.
LeetCode prepares you for algorithms. Gronex prepares you for real backend coding rounds. Practice production-style backend problems in real GitHub-like repositories — debug services, fix business logic, pass tests, and compare with real solutions, in Java, Python, and C++.
Built for SDE1+ and SDE2 backend interviews.
$ ./verify.sh
PASS OrderServiceTest.createsOrder
PASS OrderServiceTest.appliesDiscount
FAIL OrderServiceTest.processesConcurrentCheckouts
expected inventory: 0
actual inventory: -7 ← race condition
2 passed, 1 failed
Find the bug. Fix it. Make it green.Why this is different
Practice reading existing repository structure, contracts, and failing states — the rounds LeetCode and HackerRank don’t cover — instead of only writing fresh code.
Who it is for
Mid-level and aspiring mid-level backend engineers who are interviewing now, plus anyone leveling up debugging, concurrency, and code-reading.
How it works
Open a free challenge, download the watermarked starter repo, fix the failing tests locally with the bundled verify.sh, then compare against a reviewed diff.
Learn how real systems are built, one annotated diagram at a time.
Study reference architectures with detailed, full-size diagrams and clear written walkthroughs — from core building blocks to trade-offs interviewers actually probe. Included with Gronex Pro, with free guides to get you started.
Problem formats
Representative interview tasks
Launch scope