Directi interview questions and how to prepare

1. Directi's Radix manages many new gTLDs like .online and .tech. Imagine you need to design a highly available, globally distributed DNS resolution system for these TLDs that can handle peak query loads of millions per second, with sub-50ms latency for most users. Describe the core architectural components, data distribution strategy, and key considerations for fault tolerance and cache invalidation.

   Software EngineerSystem DesignTests: Evaluates understanding of distributed systems, DNS architecture, scalability, and fault tolerance at extreme scale.

2. A critical system at LogicBoxes processes domain registration requests, which involves multiple steps: checking availability, payment processing, sending to registry, provisioning DNS. If a bug causes domain registrations to randomly fail for 0.5% of users with an unclear error message, how would you approach debugging this in a production environment with millions of transactions daily? List your steps and tools you'd use.

   Software EngineerDebuggingTests: Assesses systematic debugging approach, understanding of logging/monitoring, and production troubleshooting skills.

3. Directi needs to implement a feature for Radix allowing users to purchase 'premium domains' which have higher prices and dynamic availability. Design an API endpoint for checking the real-time availability and current premium pricing of a specific domain name (e.g., 'cool.online'). Consider performance, caching, and data consistency across multiple registry systems.

   Software EngineerAPI DesignTests: Evaluates API design principles, understanding of real-time data, caching strategies, and consistency models.

4. Given a list of domain names, each with a creation date and an expiry date, and a target date D. Write a function count_active_domains(domains, D) that returns the total number of domains that were active on date D. A domain is active if creation_date <= D < expiry_date. Optimize for a very large list of domains (millions) and multiple queries for different D.

   Software EngineerCoding/AlgorithmsTests: Assesses algorithmic thinking, data structure choice (e.g., interval trees, segment trees, or sorting with sweep line), and optimization for query performance.

5. Imagine Directi's internal CI/CD pipeline for Radix's DNS infrastructure. If a new deployment causes a 10% increase in DNS lookup latency for a specific region, but only during peak hours, how would you identify the root cause and roll back/mitigate the issue quickly? Assume you have metrics dashboards and access to deployment logs.

   Software EngineerDevOps/TroubleshootingTests: Evaluates incident response, understanding of monitoring tools, and ability to correlate metrics with deployments.

6. Directi's domain registrar platforms (like LogicBoxes) need to send millions of renewal reminder emails daily. Design an asynchronous email notification system that is fault-tolerant, scalable, and allows for personalized content. How would you handle retries, rate limiting with various email providers, and ensure deliverability?

   Software EngineerSystem DesignTests: Assesses understanding of asynchronous processing, message queues, fault tolerance, and external API integration challenges.

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