ABSTRACT
Modernization of legacy applications is one of the main activitys enterprises embark in digital transformation. The chapter discusses various modernization strategies and modernization paths. The key paths to modernization are retire (decommission the applications and solution components that are not used or has little business value), retain (retain the applications that cannot be migrated), rehost (lift and shift the existing applications to a newer host), re-platform (migrate the applications into newer platform) and refactor (redesigning the existing application to a modern architecture). To reduce the modernization risk the proven best practices are to validate the migration approach using a proof of concept, iterative migration, robust planning of migration and migration process automation. The best practices of database modernization are migration to open-source databases, migration to managed databases to reduce the management cost and using the appropriate database engine fit for the use case. The best practices of services modernization are usage of open standards, usage of serverless functions, containerization, move to cloud managed services and migration to low code/no code platforms. The chapter also discusses specific modernization scenarios related to legacy Java modernization, banking system modernization, mainframe modernization, batch job modernization, OS modernization and packaged software modernization.
