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A client of ours has used a 3rd party company who charged them $300 to "speed up" their website. He is wondering if this is legitimate? In a very short period (one day), the site speed has improved from about 20 to 86 on desktop and 100 on mobile. This is on a Shopify site. As far as I can see from looking at the back end of the site, all that has been done is that a new theme has been uploaded. Nothing else has been done, eg all images look to be the same size, etc. When I asked how the work had been done so quickly, I was told "It was done by a highly professional team of Shopify web designers and developers." Has anyone come across this type of speed optimisation and can you tell me anything about it?