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Follow-up observations of high-magnification gravitational microlensingevents can fully exploit their intrinsic sensitivity to detect extrasolarplanets, especially those with small mass ratios. To make followup more uniformand efficient, we develop a system, HighMagFinder, based on the real-time datafrom the Korean Microlensing Telescope Network (KMTNet) to automatically alertpossible ongoing high-magnification events. We started a new phase of follow-upobservations with the help of HighMagFinder in 2021. Here we report thediscovery of two planets in high-magnification microlensing events,KMT-2021-BLG-0171 and KMT-2021-BLG-1689, which were identified by theHighMagFinder. We find that both events suffer the ``central-resonant'' causticdegeneracy. The planet-host mass-ratio is $q\sim4.7\times10^{-5}$ or $q\sim2.2\times10^{-5}$ for KMT-2021-BLG-0171, and $q\sim2.5\times10^{-4}$ or $q\sim1.8\times10^{-4}$ for KMT-2021-BLG-1689. Together with two events reported byRyu et al. (2022), four cases that suffer such degeneracy have been discoveredin the 2021 season alone, indicating that the degenerate solutions may havebeen missed in some previous studies. We also propose a new factor forweighting the probability of each solution from the phase-space. The resonantinterpretations for the two events are disfavored under this consideration.This factor can be included in future statistical studies to weight degeneratesolutions.

KMT-2021-BLG-0171Lb and KMT-2021-BLG-1689Lb: Two Microlensing Planets in the KMTNet High-cadence Fields with Followup Observations