Biodiversity databases are changing the longevity of data in the era of open science. They also represent a collaboration opportunity in analyzing large-scale (paleo)biological patterns beyond a local project or a time scale. Ostracods, microscopic crustaceans, are a component in many biodiversity databases. They live in most kinds of aquatic environments today and their fossil record spans nearly the whole of the Earth's metazoan biosphere history from Ordovician to Holocene. Thus, ostracods provide an ideal model system for understanding large-scale biodiversity patterns and dynamics in both space and time. Thanks to many contributors, current and future ostracodologists have access to databases that have gone through numerous improvements and have been populated by many datasets. However, rapid growth of databases has caused confusion among users regarding available data, technical terms and database aims. We review key databases that include ostracods, summarizing their history of development, current spatial and temporal coverage, various types of data models and the intertwined relationships between databases. We also present a quantitative summary of ostracod diversity history based on the Paleobiology Database. Our investigations show that the database field is transitioning from the traditional single focus to multipurpose, from static to dynamic data display/download and from independent systems to collaborative networks. We compare the ways several databases approach persistent challenges such as taxonomic harmonization, validation of the original sampling metadata and paleolocality uncertainties. With increasing capability of data integration, databases continue to require enormous efforts regarding high-quality data entry and careful coordination among scientists and technical teams.