Abstract
Large-scale software systems frequently suffer from architectural rigidity caused by monolithic designs, tightly coupled integrations, and legacy technology stacks. Backend-forFrontend (BFF) architectures are increasingly adopted to address these challenges by decoupling frontend-specific requirements from backend domain services. However, designing a BFF layer requires a series of irreversible technology decisions across compute platforms, traffic routing, programming languages, frameworks, and API protocols. These decisions directly influence system latency, scalability, operational complexity, and long-term maintainability. This paper proposes a structured, metrics-driven decision framework to guide architects through foundational technology choices when designing BFF architectures. The framework decomposes the decision space into independent sub-problems, introduces weighted evaluation criteria, and applies quantitative scoring models to enable objective trade-off analysis. The approach is validated through a representative modernization scenario, demonstrating how systematic evaluation reduces architectural risk, resolves stakeholder disagreement, and improves performance and developer efficiency. The proposed framework is generic, repeatable, and applicable to a wide range of cloudnative system modernization efforts.