I would say Not enough for how many engineers they had. It had all of the promise, and was frankly mismanaged.
They kept promoting engineers who wanted it to become an AWS service (agnostic of Amazon) rather than solving the Amazon problems at hand.
For example they built a new product identifier… Amazon did not need yet another database of products. This stuff was constantly slowing them down to less than a crawl.
Last I heard all of that was canceled, and their focus brought back to Amazon Retail only problems. But tech debt and culture issues like that are really hard to unwind.