Blog | Daniel Greener-Vigil

CS terms, interview problem walkthroughs, and architecture notes from the field.

July 10, 2026· 7 min read

Designing a Rate Limiter: Token Bucket vs. Sliding Window

A rate limiter is a small piece of state and a simple rule, but the algorithm you pick and where that state lives determines whether it actually works once you have more than one server.

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Interview Problem Walkthroughs

June 19, 2026· 4 min read

Detecting a Cycle in a Linked List: Floyd's Tortoise and Hare

Two pointers, one slow and one fast, are all it takes to detect a cycle in a linked list in O(1) space — no hash set required. Here's why it actually works, not just that it does.

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CS Terms & Concepts

May 29, 2026· 7 min read

Memoization vs. Dynamic Programming: What's the Difference?

Memoization and dynamic programming get treated as competing techniques when one is actually a form of the other. Here's the real relationship, with naive, memoized, and tabulated Fibonacci to make it concrete.

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Architecture & System Design

May 8, 2026· 10 min read

The SOLID Principles, Explained With Code You'll Actually Write

SOLID gets taught as five abstract rules and forgotten just as fast. Here they are with concrete, boring, realistic code — the kind you'd actually review in a pull request.

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Interview Problem Walkthroughs

April 17, 2026· 6 min read

Reversing a Linked List — Iterative and Recursive, With Diagrams

Reversing a singly linked list two ways, with a real explanation of the pointer surgery involved — plus why the elegant recursive version isn't always the right answer.

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CS Terms & Concepts

March 27, 2026· 7 min read

What Is a Hash Map? How It Works Under the Hood

Hash maps give you O(1) average-case lookups almost for free. Here's the hashing, bucketing, and collision handling that actually makes that possible, built from scratch.

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Architecture & System Design

March 6, 2026· 5 min read

Monolith vs. Microservices: What I'd Actually Choose as a Tech Lead

Monolith vs. microservices isn't a technology choice, it's an organizational one. A practical decision framework from someone who has led both kinds of migrations.

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Interview Problem Walkthroughs

February 13, 2026· 9 min read

Two Sum, Three Ways: Brute Force, Hash Map, Two Pointers

The classic first interview question, solved three different ways — with a real explanation of why the hash map approach wins and when the alternatives are actually the better call.

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CS Terms & Concepts

January 23, 2026· 10 min read

Big O Notation, Explained for Interviews and Code Review

A practical guide to Big O notation: what it actually measures, the complexities you'll see most often, and how to reason about them without memorizing a cheat sheet.

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