Today we continue 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
We looked at the Operational Excellence, Reliability and security pillar and we reviewed the associated best practices.
Next we review the performance-efficiency pillar which includes the ability to use computing resources efficiently even with the fluctuations in demand and as technology evolves.
It includes five design principles. These are:
Vendor aware deployments - This implies that we don't need to host and run a new technology. Databases, machine learning, encodings are best done at the cloud level by dedicated teams so that our service may simply use it.
global availability - We deploy the system in multiple regions around the world so they provide lower latency and more availability.
serverless architectures - This notion eliminates ownership of servers for the computations and storage services act as static websites. Even the event services can be used to host the code
experiment more often - with virtual and automate-able resources, we can carry out comparative , we can quickly evaluate which T-shirt size works for us
Mechanical sympathy - This calls for using the technology that best helps us to achieve what we want with our service.
 The four best practice areas in this regard are:
Selection - As wirkloads vary, the solution becomes more nuanced about the choice of products and often involves a hybrid approach to overcome trade-offs. If the choices are done on a cyclical basis.the solution improves over time
Review - This is about evaluating newer technologies and retiring older technologies  The cloud services for example become available in new regions and upgrade their services and features.
Monitoring - This gives continuous feedback on the systems as deployed so that alarms can be set in place for actions to be taken
Trade-offs- The initial design may have considered trade-offs such as consistency, durability and space versus time or latency to deliver higher performance but these also need to be done with subsequent change management
#codingexercise
Find the nth multiple of k in Fibonacci Series
solution 1 : iterate through the Fibonacci Series testing and counting success
solution 2: Fibonacci multiples of a number are periodic. depending on k determine the period and hence the position of the result.
int GetNthMultipleFibonacci (int k, int n)
{
int multiple = -1;
for (int I = 0; I  < int_max; i++)
{
if (GetFibonacci (i) % k == 0){
    multiple = i + 1;
    break;
}
}
if (multiple == -1) return -1;
int position = n * multiple;
return GetFibonacci (position);
}