  The prominent radio quasar PKS 2215+020 (J2217+0220) was once labelled as a
new laboratory for core--jet physics at redshift z=3.572 because of its
exceptionally extended jet structure traceable with very long baseline
interferometric (VLBI) observations up to a ~600 pc projected distance from the
compact core and a hint of an arcsec-scale radio and an X-ray jet. While the
presence of an X-ray jet could not be confirmed later, this active galactic
nucleus is still unique at high redshift with its long VLBI jet. Here, we
analyse archival multi-epoch VLBI imaging data at five frequency bands from 1.7
to 15.4 GHz covering a period of more than 25 years from 1995 to 2020. We
constrain apparent proper motions of jet components in PKS 2215+020 for the
first time. Brightness distribution modeling at 8 GHz reveals a nearly 0.02
mas/yr proper motion (moderately superluminal with apparently two times the
speed of light), and provides delta=11.5 for the Doppler-boosting factor in the
inner relativistic jet that is inclined within 2 deg to the line of sight and
has a Gamma=6 bulk Lorentz factor. These values qualify PKS 2215+020 as a
blazar, with rather typical jet properties in a small sample of only about 20
objects at z>3.5 that have similar measurements to date. According to the 2-GHz
VLBI data, the diffuse and extended outer emission feature at ~60 mas from the
core, probably a place where the jet interacts with and decelerated by the
ambient galactic medium, is consistent with being stationary, albeit slow
motion cannot be excluded based on the presently available data.
