Which factors affect performance of magento?

There are many factors that affects the performance of magento, but most important of them are: 

1. EAV structure of magento database, even for retrieving single entity the query becomes very complex .
2. Huge XML trees built up for layout configuration, application configuration settings
3. Magento’s template system involves a lot of recursive rendering

For improve magento performance you can do :

1) Enabled magento caching

2) MySQL Query caching

3) Enable Gzip Compression

4) Disable any unused modules

5) Disable the Magento log

6) Optimise your images

7) Combine external CSS/JS into one file

8) Enable Apache KeepAlives: Make sure your Apache configuration has KeepAlives enabled.

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