One of the most complicated and often vexed relationships in the tech business is the one between product managers and engineers. If you ask a product manager what they do, they'll often say something along the lines of 'I [lead, guide, direct, oversee] product development' or 'I come up with ideas for products'. A really good one will often put it more like, 'I'm a hub for input into the product from all the functional areas, including marketing, sales, and customer service -- then I interface with engineers to make sure the right product gets built'. Tension occurs between PM and eng when engineers push back on a product spec or (even worse) an idea that never makes it to a written spec.
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