The document discusses robust and anti-fragile design. It defines fragile as easily broken or damaged, resilient as having the capacity to maintain purpose during change, and robust as hardened against breaking but lacking resilience. Anti-fragile is defined as getting better from shocks rather than just resisting change like resilience. The document advocates designing systems that are flexible, robust, reusable, and can induce failures to reduce uncertainty and become anti-fragile. Microservices, cloud auto-scaling, and tools like Chaos Monkey that randomly induce failures are presented as ways to build anti-fragile systems.

1. Robust & Anti Fragile
Design
Lior Harel, Kenshoo

2. What’s a Bad Design?
1. Rigid
2. Fragile
3. Immobility

3. What’s a Good Design
1. Flexible
2. Robust
3. Reusable

4. Robustness Principle
“Be Conservative in what you do, be liberal in what you
accept from others”
Postel’s law - Jon Postel
(God of the Internet)

5. For Example
def add_numbers(numbers):
"""
takes in a simple array of numbers. It will then iterate
over each number,
while doing so it adds the numbers together, finally it
returns the result.
"""
sum = 0
for number in numbers:
sum += number
return sum

6. Linux/Unix Philosophy
● Robustness results from transparency and simplicity
● Rule of Composition - Small, modular programs

7. Python Zen
Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than *right* now.
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!

8. Agile…
Increase rate of change

9. But…
Is Robust the Opposite of Fragile?

10. Anti Fragile
“Anti fragile is beyond resilience or
robustness. The resilient resists shocks
and stays the same; the antifragile gets
better”
A book by Nassim Taleb

11. Definitions
● Fragile - (of an object) easily broken or damaged Merriam-Webster
● Resilient - The capacity of a system, enterprise, or a person to maintain its
core purpose and integrity in the face of dramatically changed
circumstances.
● Robust - A system or entity that has been hardened so that it is not easily
broken, while lacking the recovery abilities of a resilient system.
● Antifragile - "Beyond resilience or robustness. The resilient resists shocks
and stays the same; the antifragile gets better." Antifragile

12. Black Swan
1. The event is a surprise (to the observer).
2. The event has a major effect.
3. After the first recorded instance of the event, it is
rationalized by hindsight, as if it could have been
expected; that is, the relevant data were available but
unaccounted for in risk mitigation programs. The same
is true for the personal perception by individuals

13. Currency Rates Black Swan in Kenshoo

14. Resilient Systems
● Cloud - Auto scaling
● Mobile - No Network

15. Micro Services
(SRP anyone?)

16. Anti Fragile How To
● Create fault tolerant applications
● Regularly induce failures to reduce uncertainty

17. Netflix Simian Army
Chaos Monkey, a tool that randomly disables our production instances to
make sure we can survive this common type of failure without any customer
impact
Chaos Gorilla is similar to Chaos Monkey, but simulates an outage of an entire
Amazon availability zone.

18. Thank You...