Resolving Performance Puzzle

It is challenging for beginners to start performance tuning of an application. I was in same situation when got my first performance tuning assignment. Before starting with performance tuning we need to understand the aspects of it. 

In simple words Performance tuning is the improvement of system performance. Most systems will respond to increased load with some degree of decreasing performance. The core of performance tuning is the performance testing.

Here is the list of steps to execute systematic tuning.

1. Assess the issue, get the numbers (to baseline the performance) to measure the performance (Mostly available/defined in Non Functional Requirement [NFR] document).
2.  Measure the performance of system.
3. Identify the bottlenecks (Part of the system that is critical for performance).
4. Modify the system update/remove the bottleneck.
5. Measure the system performance after above modification.
6. In the case modification improves the performance adopt it,otherwise revert the above modification.
7. Repeat from steps 2 to 6 in cycles to improve the performance requirement.

These are high level steps. The most confusing/challenging question comes into mind is. 

Where (which part of application) to start performance testing ?.

Most of the web applications are modularized/divided into 3 major parts.

1. Database.
2. Back-end code (Including third party calls). 
3. Front-end.

Its always better to start from database and end at front-end.