This article examines the often-overlooked server-side infrastructures that sustain participatory platforms in digital democracy. Based on 40 interviews with a diverse population of digital participation professionals across four continents, the article develops a typology of three infrastructural models: private, public, and common (or public-common). One Italian and two French cases show that private solutions offer scalability and relative reliability, but at the cost of concentrated control and dependence on private cloud providers. Three examples from Mexico, Argentina, and Taiwan show that public solutions can strengthen digital sovereignty and institutional ownership, yet remain viable mainly under conditions of modest participation or strong administrative commitment. Finally, the public-common model offers the most democratic governance, but remains incomplete if it is pursued only on the software level (as in a Spanish case) without including hosting sovereignty. In light of existing communal alternatives in internet infrastructure (namely in the United States and Spain), the article shows that more democratic arrangements are possible when political will is present. It thus argues that infrastructural choices should become an explicit object of public, academic, and political debate if real digital sovereignty is to be pursued at national or continental scales.