Okta Staff Backend Engineer Interview Experience — A Token-Bucket Take-home and Cross-Domain Login

HM Screening
A conversation with the hiring manager, mainly about past project experience, behavioral questions, and various real workplace scenarios.
Take-Home Assignment
Build a rate limiter in Node.js using the token bucket algorithm.

1. Create an Express application that can read a configuration file.
2. Expose an API that returns a rate-limit response.
   Technical Round - Code Review & Debugging
   Code Review: Review the actual implementation of the rate limiter submitted earlier and explain the reasons for the particular code architecture and structure.
   Code Debugging / Optimization: Analyze and optimize a simple Node.js Express API endpoint,
   /authenticate.
3. The endpoint takes a username and password, queries the database, uses bcrypt to check the password against its hash, and returns 200 or an error.
4. Find all the missing logic, such as input validation and error handling, and add the correct HTTP status codes.
5. Change the originally synchronous bcrypt comparison to an asynchronous implementation to avoid blocking the event loop.
   System Design
   Cross-domain single sign-on design:
6. A business originally owned one domain and has recently acquired another domain.
7. After users sign in to one domain, they need to be signed in automatically to the other.
8. Design and explain the specific flow that implements this requirement.
   OIDC (OpenID Connect) multi-site login:
9. There are multiple sites that need cross-site login.
10. Within the app, users need access to certain third-party tools. Design the overall architecture and authorization flow.