Explain the difference between horizontal and vertical scaling.

Vertical scaling means increasing the resources of a single machine, such as adding more CPU or memory. It is simpler to implement but has hardware limits and can become a single point of failure.

Horizontal scaling means adding more machines and distributing the load across them. It provides better fault tolerance and scalability but introduces additional complexity such as load balancing, data consistency, and distributed coordination.

Modern high scale systems typically favor horizontal scaling because it supports elastic growth and higher availability.

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How does database indexing improve performance?

Database indexing improves performance by creating a data structure, typically a B-tree or hash based structure, that allows the database engine to locate rows quickly without scanning the entire table.

Without an index, queries often require full table scans, which are O(n). With a proper index, lookups can be reduced to O(log n) or even O(1) depending on the index type.

However, indexes come with trade offs. They consume additional storage and can slow down write operations because the index must be updated whenever the data changes. Therefore, indexes should be added selectively based on query patterns.

How do you prioritize tasks when everything seems urgent?

When multiple tasks are urgent, I first evaluate impact and urgency separately. I prioritize work that affects customers or production stability the most.

I also communicate early with stakeholders to align expectations and avoid silent trade offs. If necessary, I break work into smaller deliverables to show progress quickly.

This structured prioritization helps ensure that the most critical issues are addressed first while maintaining transparency with the team.

What about negative numbers?

What is the difference between REST and RPC?

REST is an architectural style that models interactions around resources using standard HTTP methods such as GET, POST, PUT, and DELETE. It emphasizes stateless communication and resource oriented design.

RPC, or Remote Procedure Call, focuses on invoking actions or functions on a remote server as if they were local calls. It is typically more operation focused rather than resource focused.

REST is generally preferred for public web APIs due to its simplicity and cache friendliness, while RPC based approaches like gRPC are often used in internal microservices where performance and strong contracts are more important.

How do you approach debugging a system you did not build?

When debugging an unfamiliar system, I start by understanding the high level architecture and the data flow between components.

Next, I reproduce the issue in a controlled environment and use logs, metrics, and traces to narrow down where the failure occurs. I form hypotheses and validate them incrementally rather than making broad changes.

Throughout the process, I document findings and communicate with team members who have context. This structured approach helps reduce guesswork and speeds up root cause identification.