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The James Webb Space Telescope continues to push back the redshift frontierto ever earlier cosmic epochs, with recent announcements of galaxy candidatesat redshifts of $15 \lesssim z \lesssim 30$. We leverage the recent GUREFTsuite of dissipationless $N$-body simulations, which were designed forinterpreting observations in the high redshift Universe, and providepredictions of dark matter halo mass functions and halo growth rates for astate-of-the-art cosmology over a wide range of halo masses from $6 < z< 30$.We combine these results with an empirical framework that maps halo growth rateto galaxy star formation rate and then to rest-frame UV luminosity. We findthat even if all of the photometrically selected $15 \lesssim z \lesssim 30$galaxy candidates are real and actually at these extreme redshifts, there is nofundamental tension with $\Lambda$CDM, nor are exotic explanations required.With stellar light-to-mass ratios similar to those in well-studied lowerredshift galaxies, our simple model can account for the observed extremeultra-high redshift populations with star formation efficiencies that peak atvalues of 20-65 percent. Bursty star formation, or higher light-to-mass ratiossuch as are expected for lower metallicity stellar populations or a top-heavyInitial Mass Function, would result in even lower required star formationefficiencies, comparable to values predicted by high resolution numericalsimulations of high-surface density star forming clouds.

$\Lambda$CDM is still not broken: empirical constraints on the star formation efficiency at $z \sim 12-30$