When modernizing legacy systems, don’t be afraid to build glue services

This article discusses a common challenge in modernizing legacy IT systems: the tendency to let existing integrations dictate the architecture of the new platform, leading to superficial upgrades. The author proposes using 'glue services' (formally known as anti-corruption layers) to decouple legacy protocols and dependencies from the modern internal platform. These lightweight edge services translate between old and new worlds, allowing teams to design the internal system optimally while maintaining compatibility with legacy clients and integrations. The approach reduces risk, enables gradual migration, and can be applied to both inbound and outbound integrations. Examples include translating XML/Message Brokers to gRPC, breaking files into APIs, and terminating long-lived TCP sessions at the edge. The article is a technical best-practice guide for software engineers and architects involved in system modernization.