Most of SentinelHub's open access data comes from Sentinel-1 (radar) and 2 (optical) satellites constellations, which offer a 6-days or shorter revisit time over nearly any point on Earth (for S-1, this is currently longer, as one of the two S-1 sats making up the constellation is out of order).

This is not quite high resolution data however - in the 10 to 20 meters per pixel range, i.e. medium resolution. Sentinels are not reconnaissance satellites, but are rather tasked for mapping and collecting large amounts of data globally, for which the main use cases do not necessarily need high resolution imagery (agricultural monitoring, deforestation, natural catastrophes...).

Reconnaissance satellites have much finer ground resolution (sub-meter per pixel, down to a couple dozen centimeters... from what is publicly available), and some constellations feature daily revisit cycles.