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Hectal
Roadmap
Phase 9Intermediate12 of 19 in the curriculum

Scalability

Vertical, horizontal, stateless, load balancers, CDNs, and the numbers behind it all.

Scalability is the art of handling more requests without falling over — by making machines bigger, adding machines, or making services stateless so machines are interchangeable. This phase is where HLD answers start to look like HLD answers.

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9 topics ~59 min 7 code blocks & diagrams
Start with the first topic
1
9.1

Vertical Scaling

Bigger machine: more CPU, RAM, disk, network. Simple, finite, and expensive in all the interesting ways.

7 min 1 diagram practice

2
9.2

Horizontal Scaling

More machines behind a load balancer — the scalable path that demands statelessness.

6 min 1 diagram practice

3
9.3

Stateless Services

The principle that makes horizontal scaling, rolling deploys, and instance-juggling boring.

6 min practice

4
9.4

Load Balancers

Round Robin, Least Connections, IP Hash, health checks — the front door of every scaled system.

7 min 1 diagram 1 code practice

5
9.5

CDN

Caching static (and some dynamic) content at edge nodes near users — the first latency lever at global scale.

7 min 1 diagram practice

6
9.6

Reverse Proxy

The single front door that terminates TLS, compresses, caches, and hides the fleet — Nginx's day job.

6 min practice

7
9.7

API Gateway

The L7 front door for APIs: routing, auth, quotas, aggregation, and the single integration point for clients.

6 min 1 diagram practice

8
9.8

Autoscaling

Add and remove instances by demand signals — the automation that turns capacity into a managed cost.

6 min practice

9
9.9

Capacity Estimation

QPS/RPS, storage, bandwidth, memory — the arithmetic that makes every HLD answer defensible.

8 min 1 code practice