The crisis emerging from the COVID-19 pandemic has elevated the relevance of the welfare state as well as the role of platforms and data infrastructures across key areas of public and social life. Whilst the crisis shed light on the ways in which these might intersect, the turn to data-driven systems in public administration has been a prominent development in several countries for quite some time. In this chapter I focus on the UK as a pertinent example of key trends at the intersection of technological infrastructures and the welfare state. In particular, using developments in UK welfare sectors as a lens, I advance a two-part argument about the ways in which data infrastructures are transforming state-citizen relations through on the one hand advancing an actuarial logic based on personalised risk and the individualisation of social problems (what I refer to as responsibilisation) and, on the other, entrenching a dependency on an economic model that perpetuates the circulation of data accumulation (what I refer to as rentierism). These mechanisms, I argue, fundamentally shift the ‘matrix of social power’ that made the modern welfare state possible and position questions of data infrastructures as a core component of how we need to understand social change.