"Does" vs. "do" can be a difficult distinction[2]. Your choice depends on whether the sentence subject is singular ("he does like cake") or plural ("bob and alice do like cake").
A good trick to make the distinction easier (and to properly identify the subject, which I still find difficult in some cases) is to rearrange the sentence as a simple affirmation:
* Startups does hire above 35.
* Startups do hire above 35.
The only exception to this rule is that you always use do when the subject is "I," "me," or "you": "I do," "you do," "do you?", "do I?", "do startups hire me?," etc (even though "I," "me," and "you" are singular).
1. The vibe I've gotten from HN and /r/programming (and from my own experience communicating in another language) is that, in general, ESL individuals find it helpful for others to point out when they make grammatical mistakes. Hopefully JamesAdir feels the same, and actually is ESL (or I'm sure I'll come out looking like a jackass), so I apologize in advance if the above is not true in this case. 2. http://data.grammarbook.com/blog/verbs/what-does-or-what-do/