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I know several developers but the main concern is the platform, Big Commerce. I am not offering feedback regarding the platform, but the first decision you need to make is whether you are committed to sticking with Big Commerce. If you wish to keep the site built on Big Commerce, my recommendation would be to seek out a developer who specifically has experience working with that platform. There are tons of developers and companies who are all to willing to accept any web development work. You want a specialist who can say "I have built dozens of Big Commerce sites, that's mainly what I do."