Distributed key-value stores have become indispensable for large scale low latency applications. Many cloud services have deployed in-memory data grids for their enterprise infrastructures and support multi-tenancy services. But it is still difficult to provide consistent performance to all tenants for fluctuating workloads that need to scale out. Many popular key-value stores suffer from performance problems at scale and different tenant requirements. To this front, we present our study with Hazelcast, a popular open source data grid, and provide insights to contention and performance bottlenecks. Through experimental analysis, this paper uncovers scenarios of performance degradation followed by optimized performance via end-point multiplexing. Our study suggests that processing increasing number of client requests spawning fewer number of threads help improve performance.