  Detectors at future $e^+e^-$ colliders need special calorimeters in the very
forward region for a fast estimate and precise measurement of the luminosity,
to improve the hermeticity and mask the central tracking detectors from
backscattered particles. In our concept, two compact calorimeters are foreseen,
LumiCal and BeamCal. Both are designed as sandwich calorimeters with very thin
sensor planes to keep the Moli\`ere radius small, facilitating such the
measurement of electron showers in the presence of background. Silicon sensor
prototypes and dedicated FE ASICs have been developed and produced. The ASICs
match the timing and dynamic range requirements. In the recent beam tests, a
multi-plane compact prototype was equipped with thin sensor planes fully
assembled with the new readout electronics and installed in 1 mm gaps between
tungsten plates of one radiation length thickness. The latest status of the
calorimeter prototype development will be presented, including selected
performance results, obtained in a 5 GeV electron beam at DESY, as well as the
expected performance obtained from simulation.
