A computer-implemented method for selecting digital components from a repository of digital components while securing user data, the method comprising: receiving, by a multi-platform server and from a client device, a request for a digital component for presentation by the client device, wherein the request for the digital component includes (i) request data that is opaque to the multi-platform server, and (ii) sensitive user data that is managed by the client device; in response to receiving the request for the digital component, transmitting, by the multi-platform server and to a first content platform, a contextual request that includes the request data from the client device and that does not include the sensitive user data; after transmitting the contextual request, receiving, by the multi-platform server and from the first content platform, a contextual response that includes a selection data unit for a first repository of digital components, wherein the first repository of digital components is within a trust boundary of the multi-platform server and stores digital components of the first content platform; in response to receiving the contextual response, transmitting, by the multi-platform server, the selection data unit to the first repository of digital components; after transmitting the selection data unit to the first repository of digital components, receiving, by the multi-platform server from the first repository of digital components, a plurality of digital components that satisfy the selection data unit; filtering the plurality of digital components that satisfy the selection data unit to exclude one or more digital components that do not conform to the sensitive user data received by the multi-platform server in the request for the digital component; selecting one of the digital components that remain after filtering the plurality of digital components that satisfy the selection data unit; and providing, by the multi-platform server, the selected one of the digital components for presentation by the client device. receiving, by a multi-platform server and from a client device, a request for a digital component for presentation by the client device, wherein the request for the digital component includes (i) request data that is opaque to the multi-platform server, and (ii) sensitive user data that is managed by the client device; in response to receiving the request for the digital component, transmitting, by the multi-platform server and to a first content platform, a contextual request that includes the request data from the client device and that does not include the sensitive user data; after transmitting the contextual request, receiving, by the multi-platform server and from the first content platform, a contextual response that includes a selection data unit for a first repository of digital components, wherein the first repository of digital components is within a trust boundary of the multi-platform server and stores digital components of the first content platform; in response to receiving the contextual response, transmitting, by the multi-platform server, the selection data unit to the first repository of digital components; after transmitting the selection data unit to the first repository of digital components, receiving, by the multi-platform server from the first repository of digital components, a plurality of digital components that satisfy the selection data unit; filtering the plurality of digital components that satisfy the selection data unit to exclude one or more digital components that do not conform to the sensitive user data received by the multi-platform server in the request for the digital component; selecting one of the digital components that remain after filtering the plurality of digital components that satisfy the selection data unit; and providing, by the multi-platform server, the selected one of the digital components for presentation by the client device.