The combination of Network Function Virtualization (NFV) and Software Defined Networking (SDN) allows flows to be flexibly steered through efficient processing pipelines. As deployment of NFV becomes more prevalent, the need to provide fine-grained customization of service chains and flowlevel performance guarantees will increase, even as the diversity of Network Functions (NFs) rises. Existing NFV approaches typically route wide classes of traffic through preconfigured service chains. While this aggregation improves efficiency, it prevents flexibly steering and managing performance of flows at a fine granularity. To provide both efficiency and flexibility, we present Flurries, an NFV platform designed to support large numbers of short-lived lightweight NFs, potentially running a unique NF for each flow. Flurries maintains a pool of Docker container NFs-several thousand on each host-and resets NF memory state between flows for fast reuse. Flurries uses a hybrid of polling and interrupts to improve throughput and latency while allowing multiple NFs to efficiently share CPU cores. By assigning each NF an individual flow or a small set of flows, it becomes possible to dynamically manage the QoS and service chain functionality for flows at a very fine granularity. Our Flurries prototype demonstrates the potential for this approach to run as many as 80,000 Flurry NFs during a one second interval, while forwarding over 30Gbps of traffic, dramatically increasing data plane customizability.