Leo: Your 24/7 Mock Coding Interviewer

Why Code Execution Matters for Leo

At Leo (https://leo-code.dev), we are excited to have partnered with Judge0 to enable fast, secure, and reliable code execution for hundreds of mock coding interviews conducted on our platform.

At Leo, we are focused on building a voice agentic AI for mock coding interviews that enable millions of people looking for jobs in tech to prepare for technical interviews by being in one. A robust code execution system was at the core of our design since day 1, since test case executions and live debugging are an inseparable part to a realistic, educative mock coding interview experience.

However, it is not easy to get in-browser code execution right. We prioritized several things in our design:

Security: The code execution environment must be isolated and sandboxed, such as malicious code submitted does not impact server or database health.

Low latency: Users expect to receive results of their test case submissions fast.

High availability: Every minute, there are test cases submitted by users on Leo. We want a code execution service that is almost always available with minimal outage/downtime.

Cross-language support: Leo users expect to be able to code in a variety of languages ranging from C++ to JavaScript. Our code execution service needs to support every programming language we offer, without being too much of a nightmare on the developer’s end.

Judge0 was the perfect provider of such a code execution service that we were looking for. It is an open-source framework that could be either self-hosted or hosted via remote API, decoupling the code execution service from Leo’s core infrastructure, and preventing security concerns. Its batched requests features allow low-latency and low-cost requests with guaranteed responses in under 3 seconds, and it supports more than hundreds of programming languages. It is exactly what Leo need to power mock coding interview services for hundreds of people preparing for technical interviews worldwide.

We are excited to continue our partnership with Judge0 to build the future of technical interview prep!