  The need for a privacy management layer in today's systems started to
manifest with the emergence of new systems for privacy-preserving analytics and
privacy compliance. As a result, many independent efforts have emerged that try
to provide system support for privacy. Recently, the scope of privacy solutions
used in systems has expanded to encompass more complex techniques such as
Differential Privacy (DP). The use of these solutions in large-scale systems
imposes new challenges and requirements. Careful planning and coordination are
necessary to ensure that privacy guarantees are maintained across a wide range
of heterogeneous applications and data systems. This requires new solutions for
managing and allocating scarce and non-replenishable privacy resources. In this
paper, we introduce Cohere, a new system that simplifies the use of DP in
large-scale systems. Cohere implements a unified interface that allows
heterogeneous applications to operate on a unified view of users' data. In this
work, we further address two pressing system challenges that arise in the
context of real-world deployments: ensuring the continuity of privacy-based
applications (i.e., preventing privacy budget depletion) and effectively
allocating scarce shared privacy resources (i.e., budget) under complex
preferences. Our experiments show that Cohere achieves a 6.4--28x improvement
in utility compared to the state-of-the-art across a range of complex
workloads.
