Small-scale devices enable rapid development and optimization, and while many exist for fed-batch cultures, there are few comparable devices for high cell density perfusion cultures. To address this gap, pseudo-perfusion methodologies were developed in microwell plates at mL-scale capable of achieving many of the specific characteristics of perfusion culture, including high cell density, cell retention and increased productivity. Pseudo-perfusion was achieved via sedimentation or centrifugation of 24 microwell plates prior to media exchange 1–2 times daily, generating separation efficiencies higher than 90%. Media exchanges commenced on day 3 and achieved perfusion rates of 0.5–1.8 vessel volumes per day (VVD). Pseudo-perfusion methodologies resulted in maximum viable cell densities (VCDs) of up to 42 × 106 cells mL-1, 4.2-fold greater than fed-batch cultures. Volumetric productivities increased by 1.9-fold, generating industrially relevant productivities. Similar performance was observed between sedimentation and centrifugation methodologies, with minor deviations attributed to elongated manipulation times and lower packed cell density prior to separation when sedimentation was used. The microwell plate (MWP) experiments were validated at the 5 L scale and showed comparability in metabolite and growth profiles. The work presents the development of a robust tool for high-throughput development studies which is sensitive to changes in media composition and exchange rate, which could be reliably used for initial screening of high cell density perfusion cultures.