When driving from 3.3V -> 5V, it depends on the device if it will (reliably) work or not, and you can look this up in the datasheets.
First, for the 3.3V device, look up "output high voltage" (VOH) and "output low voltage" (VOL). In case of the axoloti:
VOH >= (VDD - 0.4) = 2.9V (for 3.3V supply)
VOL <= 0.4V
This means the axoloti will output at least 2.9V when high, and at most 0.4V when low.
For the 5V device, you have to look for "input high voltage" (VIH) and "input low voltage" (VIL). For many devices, it will be something like (CMOS standard):
VIH >= 0.7*VDD = 3.5V (for 5V supply)
VIL <= 0.3*VDD = 1.5V
This means that the chip needs to see at least 3.5V to guarantee it interprets it as high. That is a problem, because axoloti only guarantees to output 2.9V. Of course in practice axoloti might output more (close to 3.3V), and the 5V chip might be more sensitive, so it just might work in some situations. But that is not really a solution, because when for example the temperature changes it might change the levels and stop working.
For the low state this example would work, because the axoloti outputs at most 0.4V, and the target chip accepts anything below 1.5V as low.
Some 5V chips have much better characteristics, for example VIH >= 2.0 V is common (TTL standard), which the axoloti will easily drive.
So, in conclusion, you need to look at the datasheet