There are several options that may help you to speed up site. Try them out first.
Moving images to file system. For v.3.5.x and 4.0.x
For each image you want to display, a separate connection has to be opened to your database. Even if it's only one image per page, doubling the connections to the database isn't fun to think about.
Each time you do <img src="image.php?imageid=345"> or something similar, that's a separate request to the server, with PHP going to receive that image from the database. Even if you do use scripting to grab images from a non-public branch of your file tree, just using file reading creates very, very little overhead, while hitting the database creates a lot. Just connecting to the database alone, without any queries, is something which already takes a significant amount of server time (more in the sense of processing cycles than actual time).
Storing your images in database tables is not recommended from the performance point of view. Our advice is to place images into the file system. It can easily be done by modifying a single setting in the control panel. For details, study X-Cart:Images Location Management page.
After that modify original .htaccess file (in /files directory) and change the code to:
<FilesMatch "\.(gif|jpe?g|png|GIF|JPE?G|PNG|)$"> Allow from all </FilesMatch> Deny from all
Toggling off tracking statistics
It is strongly recommended you disable all the modules and functions that you do not need. If you experience problems with X-Cart performance, one of the first things you should do is disable the module Advanced Statistics. This module significantly slows down X-Cart by storing statistical information in the database.
In X-Cart v3.5.x or later:
Advanced Statistics can be disabled via the 'Modules' section of X-Cart's Admin area.
In X-Cart v3.4.x:
in the customer/auth.php file, make the line
Cleaning statistics tables
For v.3.5.x and 4.0.x.
In the admin back-end of x-cart: ‘Summary’ page - > ‘Statistics clearing’.
For v.4.1.x: Statistics can be cleared via admin area: 'Summary' page, section 'Tools/Statistics clearing'.
Optimizing SQL tables
X-Cart stores its data in database tables, and over time these tables may become fragmented/less organized. This is especially true if you make changes to the data in your store's database tables directly.
In X-Cart v.4.1.x or later:
X-Cart provides a tool that allows you to defragment the database and reclaim the unused space: 'Optimize tables'. For details on using this tool, see X-Cart: Advanced Tools page.
In X-Cart v.3.5.x and 4.0.x:
Execute the following sql query for each x-cart table
OPTIMIZE TABLE <table_name>;
where replace <table_name> with the name of a table. You will find the list of x-cart tables using the next sql query:
Generating HTML catalog
Additionally, it is advisable to create HTML catalog. After generation of HTML catalog, your customer zone is presented as a set of static pages linked together without actual PHP scripts execution and database queries. It may significantly lower loading of your server.
Compression of html source
You may try to put the following lines in the php.ini file:
output_handler = zlib.output_compression = On zlib.output_compression_level = 1
You can put any figure in the compression level between -1 and 9, just muck around and see what works best for your particular store.
Or if you are using Apache server and .htaccess files are enabled you may try to add
php_flag zlib.output_compression On
to the .htaccess in the store root.
Installing Zend Optimizer
The Zend Optimizer is a free application that runs the files encoded by the Zend Encoder and Zend SafeGuard Suite, while enhancing the running speed of PHP applications. Many scripts require that you have Zend Optimizer installed so you are able to run them on your server while decrypting and running them on-the-fly while increasing runtime performance.
Install additional Apache modules (optional)
The idea behind GZIP-encoding documents is very straightforward. Take a file that is to be transmitted to a Web client, and send a compressed version of the data, rather than the raw file. Depending on the size of the file, the compressed version can run anywhere from 50% to 20% of the original file size.
In Apache, this can be achieved using Content Negotiation, which requires that two separate sets of HTML files be generated: one for clients who can handle GZIP-encoding, and one for those who can't. This solution sends gzip-encoded files to clients who understand them, but does not allow for the compression of dynamically-generated pages.
A more graceful solution is the use of mod_gzip, one of the many additional modules available for Apache. We consider it one of the overlooked gems for designing a high-performance Web server. Using this module, configured file types will be compressed using GZIP-encoding after they've been processed by all of Apache's other modules, and before they're sent to the client. The compressed data that's generated reduces the number of bytes transferred to the client, without any loss in the structure or content of the original, uncompressed document.
Slow down SE crawlers
Search engines may crawl your site and cause a performance degradation. You may slow down the robots crawling your site by adding the following line into robots.txt file (in the root of your web site):
User-Agent: * Crawl-Delay: 10