The current best bound is due to Holmsen, Mojarrad, Pach, and Tardos [HMPT20],
who prove
$$
f(n) ≤ 2^{n+O(\sqrt{n\log n})}.
$$
[HMPT20] Holmsen, Andreas F. and Mojarrad, Hossein Nassajian and Pach, János and Tardos, Gábor,
_Two extensions of the Erdős-Szekeres problem_. J. Eur. Math. Soc. (JEMS) (2020), 3981-3995.
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