When I checked this post, you were below zero - I&#x27;m not sure why you are downvoted.<p>In any case, my main point isn&#x27;t that that WhatsApp is simple.  When I said the parent posted was being reductionist, I was referring to Twitter&#x27;s product offering. AFAIK (I could be wrong) WhatsApp is a messaging backend and multiple client frontends. The &quot;50&quot; engineers is deceiving becaus, despite the fact that Mnesia could or couldn&#x27;t have scaled, there is a very non-trivial amount of engineers who worked on it and Mnesia is a <i>good &amp; proven</i> system. In a similar light, Instagram was 13 engineers (or was it employees) and hundreds of django instances - and that maybe all you need for a photo feed, however Instagram didn&#x27;t have a trending feature until <i>earlier this year</i> and how knows how many engineers that took.<p>If WhatApp hired another 200 engineers, likely 195 would either be twiddling their thumbs or working on new features outside what was needed in that acquisition to Facebook. Now we can make the argument that Twitter is bloated because they have too many products (Fabric, Vine, Crashlytics, and their numerous other acquisitions) - and the scaling back of those engineers may mean sunsetting those products - and thats fair. To imply they have 4000 engineers building a glorified 140-char mailing list is not.