Inspiration
What it does
How we built it
Challenges we ran into
Accomplishments that we're proud of
What we learned
What's next for Cadra
Inspiration
Technical interview practice is hard to schedule and harder to repeat. Cadra gives job seekers a place to answer aloud and practice the same question again with specific feedback.
What it does
Candidates choose a recruiter or system design interview, speak with an AI interviewer, and sketch their design on a shared whiteboard. Feedback uses their answers and saved diagram. In PayPal Sandbox, a $5 test purchase adds 60 practice minutes. Cadra meters connected interview time and releases the unused reservation when a candidate finishes early.
How we built it
Cadra uses Next.js, FastAPI, and PostgreSQL. PayPal Orders v2 creates and captures sandbox purchases. Cadra verifies the capture before crediting the balance. OpenAI powers the live voice interviewer and evidence-based feedback.
Challenges and lessons
Checkout can be revisited, and a voice call can end early or disconnect. We designed the balance to credit each purchase once and settle usage from the interview connection state. In the demo, a $5 test purchase adds 60 minutes and the filmed system design interview uses 41 seconds. The video labels its feedback example from a separate take.
