CodeIgniter's main features are:

 Model-View-Controller Based System
 Extremely Light Weight
 Full Featured database classes with support for several platforms.
 Active Record Database Support
 Form and Data Validation
 Security and XSS Filtering
 Session Management
 Email Sending Class. Supports Attachments, HTML/Text email, multiple protocols (sendmail, SMTP, and Mail) and more.
 Image Manipulation Library (cropping, resizing, rotating, etc.). Supports GD, ImageMagick, and NetPBM
 File Uploading Class
 FTP Class
 Localization
 Pagination
 Data Encryption
 Benchmarking
 Full Page Caching
 Error Logging
 Application Profiling
 Calendaring Class
 User Agent Class
 Zip Encoding Class
 Template Engine Class
 Trackback Class
 XML-RPC Library
 Unit Testing Class
 Search-engine Friendly URLs
 Flexible URI Routing
 Support for Hooks and Class Extensions
 Large library of "helper" functions

 Webservice:A software system designed to support interoperable machine-to-machine interaction over a network. 

There are a number of ways in which we can bulid a web service:
a.      Remote Procedure call with XML-RPC
b.     Representational State Transfer with RESTful method

A bottleneck is part of application that is slower than the other parts, and that is slowing down the application as a whole. Here are a number of different types of bottlenecks:
 Database
API
Bandwidth
Static
Code

Benchmarks let us log the time it takes for a part, or multiple parts, of our application to run. Once we have benchmarked our application, we can generate a report to see the timings of our application wherever we set a benchmark. We can then seek out any bottlenecks in our application, and rectify them.

CodeIginter provides a number of security options to handle to our applications:
a. URL security
b, Global security
c. Filtering data
d. Password salting
e. Database security
f. Cross-site scripting