Purpose: This paper systematically reviews the implementation of Zero Trust (ZT) Architecture, focusing on the critical challenges associated with its deployment and, specifically, the nuanced trade-off between enhanced security and user-perceived usability friction. It aims to synthesize the current state of practice and identify the core arguments that are shaping the next generation of adaptive access control.

Methodology: A systematic literature review was conducted, synthesizing academic and industry documentation on ZT principles, architectural components, and empirical studies concerning user experience. The analysis utilized a novel Security-Usability Trade-Off (SUT) Matrix to map findings related to security strength against metrics of user friction, such as security fatigue and productivity effects.

Findings: The findings confirm that ZT represents a fundamental paradigm shift from network-centric to identity-centric access control, leveraging real-time, continuous authentication attributes. A significant implementation barrier is the human element, where increased multi-factor authentication (MFA) requirements often lead to observable security fatigue and employee resistance. The most effective ZT models are those that integrate context-aware machine learning into the Policy Decision Point for truly adaptive, low-friction boundary enforcement.

Originality: This study provides a unified conceptual framework for evaluating ZT implementation success that moves beyond purely technical metrics to incorporate essential human factors. It proposes the "Frictionless ZT" model as a necessary path for maximizing compliance and minimizing organizational cost associated with security fatigue.