  We analyzed an observation with the Nuclear Spectroscopic Telescope Array of
the black-hole X-ray binary MAXI J1535-571 in the soft intermediate state, in
which we detected a 2.5-ks long flare. Our spectral fitting results suggest
that MAXI J1535-571 possesses a high spin of 0.97 (-0.10/+0.02) and a low
inclination of approximately 24 deg. We observed a gradual increase in the
inner disc radius, as determined from fits to the continuum spectrum. This
trend is inconsistent with an increased flux ratio of the thermal component, as
well as the source evolving towards the soft state. This inconsistency may be
attributed to a gradual decrease of the color correction factor. Additionally,
with a flare velocity of approximately 0.5 c and a higher hardness ratio during
the flare period, the quasi-simultaneous detection of a type-B QPO in the
Neutron Star Interior Composition Explorer data, and quasi-simultaneous ejecta
launch through radio observations collectively provide strong evidence
supporting the possibility that the flare originated from a discrete jet
ejection.
