I'm having a problem with an online store. The TTFB is really big, on index page about 6 secs, in product catalog more than 10 secs. The website has many extensions/modules.
As far as my testing goes I figured out that on pages that load one or more products the TTFB increases drasticaly. But on the login page, where there are no products the TTFB is still big, around 4 secs.
I've tried putting the site on localhost on a Synology server... the TTFB decreased a bit about 30% on all pages, but still too big.
I tested a blank page with only the .js and .css files, no html in it and I still got 1-2 secs TTFB on localhost.
Disabling some of the extensions (ie. AW_Autorelated module) reduced TTFB with 2-3 secs.
I don't know what to try next. Any ideas?
Try to assign a default theme to your store and test the speed. A crappy coded theme can really screw up the store speed. If that will not help, disable all the extensions and test the speed - if the store will still be slow with the default theme and no extensions - your hosting sucks. After this, you will have a good idea if your performance issue is from the hosting configuration, theme or one of the extensions. Start enabling extensions one by one to see which one affects the speed the most. You can do this on a development copy of your store to avoid any downtime in production.
Hope this helps.
Finestshops is dead on in terms of determining the problem.
Based on you mentioning localhost, are you hosting it locally? Or was that just for testing? Generally residential (and even most business) DNS is quite terrible and could easily cause a massive TTFB.
With that aside, you mentioned disabling some extensions and seeing some improvement. With that in mind I would highly suggest you setup a good cache such as Varnish or LiteSpeed's LiteMage Cache. Having a decent cache system in place will drastically lower the TTFB in most cases.