The fear of the cloud migration
Scaling digital brands inevitably hit the limits of their legacy monolithic applications. During peak traffic events, a single bottleneck (like a heavy reporting query) can crash the entire application.
However, a 'big bang' rewrite—attempting to rebuild and deploy the entire application at once—is statistically highly likely to fail, causing massive downtime and data corruption.
The Strangler Fig pattern
Akshora AI Labs approaches monolithic migrations using the Strangler Fig pattern. Instead of a hard cutover, the new cloud-native architecture slowly replaces the old one, route by route.
- The API Gateway: An API Gateway (like Kong or NGINX) is placed in front of the legacy application. Initially, 100% of traffic is routed to the old monolith.
- Containerization: We isolate a single, low-risk feature (e.g., the user profile service), rewrite it as a microservice, containerize it with Docker, and deploy it to a Kubernetes cluster (like AWS EKS).
- Incremental Routing: The API gateway is updated to route only requests for `/api/profile` to the new Kubernetes pod, while all other traffic remains on the monolith.
- Validation: If the new microservice fails, the routing rule is instantly reverted. If it succeeds, the team moves to the next feature.
Managing state and databases
The hardest part of a migration is the data layer. Microservices require independent databases, but legacy apps use a single shared database.
During the transition, we employ data replication patterns. The new microservice might read from its own isolated PostgreSQL database, while a background CDC (Change Data Capture) tool like Debezium keeps it synchronized with the legacy monolith's database until the monolith is finally retired.
Continuous Integration & Deployment (CI/CD)
A Kubernetes migration is useless without automated deployment. We implement GitOps pipelines using tools like ArgoCD or GitHub Actions. When a developer pushes code, the pipeline automatically runs tests, builds the Docker image, and updates the Kubernetes manifests, enabling multiple safe deployments per day.