Reliability, Scalability & Maintainability

Описание: You built a viral app. It works perfectly on your laptop. But you deploy it to a million users, and it instantly becomes a nightmare. Here are the Three Pillars that save you.

Welcome to Day 14 of "100 Days of System Design." Today, we are breaking down Chapter 1 of Designing Data-Intensive Applications to look at the three pillars that hold up every massive tech architecture: Reliability, Scalability, and Maintainability.

Pillar 1: Reliability (Fault vs. Failure) ⚡
We start in our vibrant minimalist vector style. Imagine a cute, pulsing blue server doing its job. Suddenly, it gets struck by neon yellow lightning. That is a hardware Fault. But instantly, a backup server jumps in to catch the glowing data orbs before they drop. The user never sees an error. That means zero Failure. We explain how to engineer systems that anticipate their own destruction.

Pillar 2: Scalability & The Twitter Problem 🐦
How do you define scale? You have to define your "Load Parameters." We look at Twitter's infamous "Fan-out" problem. Imagine Selena Gomez sends one tweet. A glowing data packet hits the server, and suddenly explodes into 50 million smaller glowing orbs sent to all her followers at the exact same second. How do you design an architecture that survives that blast?

Pillar 3: Maintainability (The Silent Killer) 🧶
But wait, here is the silent killer. 80% of an app's cost is in maintenance, not creation. Imagine a messy, tangled ball of red wires. That is legacy code. We describe the magic of architecting a system so that the tangled mess snaps into a clean, color-coded, glowing grid (Operability, Simplicity, Evolvability).

Architecture is just balancing these three pillars. But how do you know how many servers you actually need? Tomorrow for Day 15, we learn the ultimate interview cheat code: Back-of-the-Envelope Estimation.

References:

Designing Data-Intensive Applications by Martin Kleppmann (Chapter 1)

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