A-321 First Officer reported a brake temperature warning in the descent; and the crew slowed the aircraft speed to extend the landing gear. The aircraft landed and fire rescue indicated no excessive brake temperature thereby indicating a probable indicator malfunction.

Narrative

While descending on the ZZZZZX arrival into ZZZ; just before crossing the ZZZZZ1 intersection; approximately at FL250 we received a master caution. This was associated with a ECAM for Brakes Hot. As the pilot monitoring; I called it out; confirmed it; and cancelled the master caution. The Captain and I noticed the temperature on the right inboard wheel to be 450°C. While in the descent; and at a speed of approximately 280 kts.; we did not lower the gear to cool the brakes. As the readout and subsequent hydraulic status did not make sense. The brake temperatures fluctuated between 305° and 450°C and we did not observe any abnormalities within the hydraulic pressure. The next fix on the arrival had a speed restriction of speed of 250 kts. The Captain and I agreed that it must've been a malfunctioning temperature sensor on the right inboard wheel; as the right outboard wheel was temperature was indicating a normal temperature of 30°C. Just prior to the 250 kt. speed restriction; the brake temperature on the right inboard wheel/brake jumped up to 1000°C. When this happened; the temperature readout was replaced with two amber X's. After this happened I advised ATC and asked to slow below 250kts; in order to drop the landing gear. With the unknown status/condition of the right inboard brakes/wheel; l requested that ARFF (Airport Rescue and Firefighting) be available upon landing to inspect. When this request was made; ATC requested priority handling for us and requested FOB (fuel on board) and TSOB (total souls on board). While working through the QRC; ECAM; QRH; and ECAM Supplemental procedures; we inadvertently deviated from altitude and air speed restrictions on the arrival. These deviations were solely attributed due to pilot workload. After the ZZZZZ2 intersection; we were given a descent to 4000 feet which was input and confirmed on the FCP. The Captain forgot to pull the knob to initiate the descent. After confirming the altitude; I diverted my attention to other tasks; and did not catch the Captain not pull the altitude knob to initiate the descent to 4000'. After a minute or so; ATC inquired if we were beginning the descent. At that point; we recognized the error and started the decent to 4000'. The Captain landed without incident. We exited the runway at 1. I communicated with ARFF as they inspected the right main landing gear. We were informed that there was no excessive heat; fire; or structural damage. We made the decision to have ARFF follow us our gate. The Captain shut down the aircraft and submitted a logbook entry.