Today we resume our discussion on the AWS papers in software architecture which suggests five pillars:
- Operational Excellence for running and monitoring business critical systems.
- Security to  protect information, systems, and assets with risk assessments and mitigation strategies.
- Reliability to  recover from infrastructure or service disruptions
- Performance Efficiency to ensure efficiency in the usage of resources
- Cost Optimization  to help eliminate unneeded cost and keeps the system trimmed and lean.
The guidelines to achieve the above pillars include:
1. Infrastructure capacity should be estimated not guessed
2. Systems should be tested on production scale to eliminate surprises
3. Architectural experimentation should be made easier with automation
4. There should be flexibility to evolve architectures
5. Changes to the architecture should be driven by data
6. Plan for peak days and test at these loads to observe areas of improvement
In AWS, the architecture is set by individual teams that demonstrate best practice. These guidelines are driven by data to build systems at internet scale  and shared with virtual team of principal engineers who peer review each other's designs and showcase them. This is re-inforced with the following:
First, the practices focus on enabling each team to have this capability
Second, the mechanisms that carry out the automated checks ensure that the intentions are met
Third the culture works backs from the value to the customer across all roles.
The internal review processes and the mechanisms to enforce compliance are widely adopted
We will start reviewing the guidelines in greater detail but let us take a moment to take note of the push back encountered for such initiatives:
Teams often have to get ready for a big launch so they don't find time
Even if they did get all the results in from the mechanisms, they might not be able to act on it
Sometimes the teams don't want to disclose the internal mechanisms.
In all of the above, the shortcomings are fallacious.
#codingexercise
Find the Jacobsthal number
uint GetJacobsthal(uint n)
{
if (n == 0) return 0;
if (n == 1) return 1;
return GetJacobsthal(n-1) + 2 * GetJacobsthal(n-2);
}
0 1 1 3 5 11 ...
While Pascal's triangle forms from diagonal bands of Fibonacci numbers, Jacobsthal numbers also forms computed values from adjacent numbers along the diagonals.