The document discusses domain-driven design approaches for migrating a monolithic application to microservices. It describes dividing a monolithic domain into sub-domains which become microservices, with an ecommerce domain divided into products, buyers, sellers, orders, and payments services for example. Decomposition design patterns break down an application into smaller services by business capability. Domain-driven design breaks the domain model into sub-domains which each have their own model and scope. The document also discusses using vine and strangler patterns which divide a system into smallest units, modernizing each unit as a microservice while strangling the relative legacy parts of the monolith.

1. Domain Driven Development (DDD)
Mr. Subramanyam Tirumani Vemala
https://www.linkedin.com/in/subbulinkedin/

2. Modernizing an Monolithic Application/
Migrating to Microservices from Monolithic:
Domain-Driven Design:
• Domains and Sub-Domains.
• Dividing the Monolithic (Domain) architecture into Sub-domains to
make them as Microservices.
• Works on Decomposition design pattern.
• (Ex.: Domain: E-commerce, Sub-Domain: products, buyers, sellers,
orders, payments etc.)
• (Domain = Context, Sub-Domain: Bounded context)

3. Decomposition Design Patterns:
• To decompose a small or big application into small services, you can
use the Decomposition patterns.
• An e-commerce application, then you can have separate services for
orders, payment, customers, and products if you decompose by
business capability.
• You can use the Domain-Driven Design through which the whole
domain model is broken down into sub-domains. Then, each of these
sub-domains will have their own specific model and scope (Bounded
context).

4. Decomposition: Vine Pattern or Strangler
Pattern.
• No complete replacement.
• Divide the system into smallest units called as Vines.
• Modernize/ migrate each unit into a microservice.
• Strangle the relative legacy part of the monolithic application, which
has been modernized.
• Do the modernization or migration in phases replacing the each Vine
and strangle the legacy monolithic part of the vine which is migrated.