Monolith to Microservices Migration Consulting

Martin Fowler advises against starting a new project with microservices, and reports that almost all the successful microservice stories started with a monolith that got too big and was broken up.

Martin Fowler's "Monolith First" (3 June 2015) reports that almost all the successful microservice stories started with a monolith that got too big and was broken up, and that systems built as microservices from the start have usually run into trouble.

Fowler describes his advice as tentative because the evidence is limited, and notes that some colleagues favor starting with microservices, especially teams that have done it before.

The successful stories Fowler describes began with a single application that worked and had grown too large. In Company A, a month of bug fixing and an Angular upgrade came first, and engineering cost fell from $48K to $8.7K a month.

Because the evidence behind the monolith-first advice is limited, the order is a choice to make for your own system. A team that has already run microservices in production is in a different position from a team doing it for the first time.

Company B's first version cost about $15K but was so buggy it could not deliver key features, so a team of American contractors rewrote it. That second version cost about $37K a month for three years, about $1.3M in total, and was still unstable and unmaintainable. Both versions had no proper application architecture.

Repairing the second version would have cost more than rebuilding it. I rebuilt the backend and frontend over 14 months and kept about a quarter of the existing code. Maintenance dropped below $8K a month, then to under $2K a month.