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'''Building a scalable cloud infrastructure''' requires careful planning across multiple layers — from compute and networking to storage and monitoring. This guide covers the key architectural patterns that allow your infrastructure to grow with demand.

== Scalability Fundamentals ==

There are two approaches to scaling:

* '''Vertical scaling (scale up)''' — adding more CPU, RAM, or storage to an existing server
* '''Horizontal scaling (scale out)''' — adding more servers and distributing the load

Horizontal scaling is generally preferred because it provides redundancy and has no single-machine limits.

== Load Balancing ==

A load balancer distributes incoming traffic across multiple backend servers.

=== Types of Load Balancers ===

* '''Layer 4 (TCP/UDP)''' — routes based on IP and port, very fast
* '''Layer 7 (HTTP/HTTPS)''' — routes based on URL path, headers, cookies — more flexible

=== Popular Solutions ===

* '''Nginx''' — lightweight, widely used as reverse proxy and L7 load balancer
* '''HAProxy''' — high-performance L4/L7 load balancer
* '''Cloud LB''' — managed solutions from cloud providers

=== Basic Nginx Load Balancer ===

 upstream backend {
     least_conn;
     server 10.0.1.1:8080;
     server 10.0.1.2:8080;
     server 10.0.1.3:8080;
 }

 server {
     listen 80;
     location / {
         proxy_pass http://backend;
     }
 }

== Auto-Scaling ==

Auto-scaling automatically adjusts the number of servers based on demand:

* '''Metric-based''' — scale when CPU, RAM, or request count exceeds thresholds
* '''Schedule-based''' — scale up during known peak hours
* '''Predictive''' — use historical data to anticipate demand

With [[Docker and Kubernetes: Getting Started|Kubernetes]], auto-scaling is built in via the Horizontal Pod Autoscaler (HPA).

== Content Delivery Network (CDN) ==

A CDN caches your content at edge locations worldwide, reducing latency and server load:

* '''Static assets''' — images, CSS, JavaScript, fonts
* '''Full-page caching''' — for content that changes infrequently
* '''Video streaming''' — distributed delivery for media content

Popular CDN options include Cloudflare, Fastly, and BunnyCDN. A CDN can reduce origin server load by 60–90%.

== Database Replication ==

Databases are often the bottleneck. Replication strategies include:

=== Read Replicas ===

* Primary server handles writes
* One or more replicas handle read queries
* Suitable when reads far exceed writes (most web applications)

=== Multi-Master ===

* Multiple servers accept writes
* More complex conflict resolution
* Useful for geographically distributed setups

=== Caching Layer ===

Add Redis or Memcached between your application and database:

* Cache frequently accessed data
* Reduce database query load by 80%+
* Sub-millisecond response times

== Infrastructure as Code ==

Manage your infrastructure programmatically:

* '''Terraform''' — provision servers, networks, DNS across any provider
* '''Ansible''' — configure servers and deploy applications
* '''Docker Compose / Kubernetes''' — define application topology

This ensures reproducibility and makes scaling a matter of changing a number in a configuration file.

== Monitoring and Observability ==

You cannot scale what you cannot measure:

* '''Metrics''' — Prometheus + Grafana for CPU, RAM, disk, network monitoring
* '''Logs''' — ELK stack (Elasticsearch, Logstash, Kibana) or Loki for centralized logging
* '''Alerts''' — set up notifications for anomalies before they become outages

== See Also ==

* [[Docker and Kubernetes: Getting Started]]
* [[Optimizing Website Performance with Dedicated Servers]]
* [[Cloud Computing Explained: From Basics to Advanced]]

[[Category:Cloud Computing]]