> Another example that comes to mind is a backend rewrite of a multi million PHP API to a Java backend. They just put the new Java backend in front of the old API and proxied through while they implemented the new routes. While it took over 2 years in total, it went relatively well.
Their next example was exactly what you asked for, 2 years rewrite.
Bonus points from me because they didn't wait for the whole rewrite to be done, and instead started using the new project by replacing only parts of the original one.
If you are not architectured around the bridge it is really hard to add it latter. Probably the biggest advantage of micro services is they have built in bridges. Monoliths often have no obvious way to break things up. Every time you think you want to you discover some other headache.
Their next example was exactly what you asked for, 2 years rewrite.
Bonus points from me because they didn't wait for the whole rewrite to be done, and instead started using the new project by replacing only parts of the original one.