Data centers are the most critical infrastructure of companies demanding higher and higher levels of quality of service (QoS) in terms of availability and scalability. At the core of data centers are multi-tier architectures providing service to applications. Replication is heavily used in this infrastructure for either availability or scalability but typically not for both combined. Additionally, most approaches replicate a single tier, making the non-replicated tiers potential bottlenecks and single points of failure. In this paper, we present a novel approach that provides both availability and scalability for multi-tier applications. The approach uses a replicated cache that takes into account both the application server tier (middle-tier) and the database (back-end). The underlying replicated cache protocol fully embeds the replication logic in the application server. The protocol exhibits good scalability as shown by our evaluation based on the new industrial benchmark for J2EE multi-tier systems, SPECjAppServer.