When one caliper fails, a common question is whether you must replace both on that axle. It is often recommended, though not always required. Here is the thinking on replacing calipers in pairs.
The case for pairs
Replacing both calipers on an axle keeps braking even side to side - a fresh caliper on one side and a tired one on the other can brake unequally and pull; see pull when braking. On high-mileage cars, if one seized, the other is often close behind.
When one is acceptable
If the car is newer and the other caliper is proven healthy (moves freely, no leak, even pad wear), replacing just the failed side can be fine. Unlike rotors, calipers do not have a matched-surface issue, so a single replacement will not by itself cause a pulsation.
Always do pads and rotor with it
Whether you do one caliper or both, replace the pads and service the rotor on that corner - a sticking caliper usually damaged them; see replace rotors in pairs. A loaded caliper makes the job quick; see loaded caliper.
Bottom line
Pairs are the safe default for even braking, especially on older cars; a single is acceptable when the other side is genuinely good. Fit quality pads and hardware.