I recently noticed how crazy high your passive perception can get.
Assuming you are a druid or cleric (i.e. Wisdom being your main stat) with one level in rogue, you can get expertise in perception (2*6 prof bonus). At level 20, with +5 WIS modifier, and with the Observant feat (another +5), that equals to
10 + 5 (WIS) + 12 (prof) + 5 (Observant) = 32 passive perception (+17 to checks)
As a DM, I can hardly make every perception check a DC35 (and shouldn't, since the player would have to invest quite the amount of resources to get such a high passive perception, which should be rewarded).
However, I still might want to add some traps or sneaking enemies without them being immediately spotted. How could I do this, aside from separating the master of perception from the rest of the group every time?