add scale

cspell_dict_bash.txt

@@ -561,4 +561,6 @@ UDPPORT
 
 Rickard
 
-untracked
+untracked
+
+cloudflare

docs/source/index.rst

@@ -97,6 +97,7 @@ The organization of this site is as following:
    reference/devops/set-up-debian-server-on-digital-ocean
    reference/devops/debian-firewall-nftables-and-iptables
    reference/devops/bind-dns-server-setup
+   reference/devops/scale
 
 
 .. toctree::

docs/source/reference/devops/scale.md

@@ -0,0 +1,56 @@
+# Scale
+
+## Complexity
+
+Less is more.
+
+Reduce complexity at all costs.
+
+Over-engineering is one common sources of complexity.
+
+* over-complicated solutions
+* over-complicated designs (too many classes and objects)
+* trying to predict the future
+* ...
+
+Keep scalability in mind when designing, developing, and deploying.
+
+## Scale Cube
+
+[The Scale Cube | AKF Partners](https://akfpartners.com/growth-blog/scale-cube)
+
+![](https://upload.wikimedia.org/wikipedia/commons/8/82/AKF_Scale_Cube.gif)
+
+* x-axis: duplication, such as application code and database
+  * easiest to achieve, just make copies
+* y-axis: split by verbs and nouns
+  * focus on the "final" verbs that operate on the data directly
+* z-axis: split by properties of things, like hash-value of data
+  * data of users from region A are stored in a database near region A
+
+## Vertical or Horizontal Scaling
+
+* Vertical: scale up
+  * add more resources to an system
+* Horizontal: scale out
+  * add more machines
+
+Prefer scale-out
+
+Use more and cheap devices.
+
+* Cheaper to maintain
+* Easier to scale
+* Less time to fix
+
+Use more multiple data centers.
+
+* Consider load balancing, disaster recovery, networking, speed, cost
+* [What is a Data Center? | Cloudflare](https://www.cloudflare.com/learning/cdn/glossary/data-center/)
+* [Backup site - Wikipedia](https://en.wikipedia.org/wiki/Backup_site#Hot_Sites)
+
+Use cloud smartly. Easy to set up and shut down as soon as we are done.
+
+* QA
+* batch processing
+* pike load