As online shopping booms, venture investment in the e-commerce sector has taken off. That has put a spotlight on the small software companies that power online shopping, from enabling product subscriptions to making merchants’ websites run faster. These include firms such as Fabric, Nacelle, Shogun and ReCharge.

In the first quarter of this year, VC firms invested $11.6 billion in the e-commerce sector, which includes emerging software platforms, up four times from the same period last year, according to CB Insights. Helping drive the interest is the wide variety of possible customers. It’s not just e-commerce retailers they’re targeting but companies that make clothing, shoes and other consumer items.