Cloud migration without stopping the operation: how zero-downtime migration works
One of the biggest fears of any company when planning a cloud migration is the possibility of stopping the operation during the process. The good news is that, with the right planning, it is possible to migrate critical systems to AWS without downtime perceptible to the end user. Understand how this works in practice.
Why does traditional migration usually require downtime?
In the simplest migration model, the system is shut down in the old environment, the data is transferred, the new environment is validated, and only then does the system come back online in the cloud. This process can take from minutes to several hours, depending on the volume of data and the complexity of the application, and any downtime during this period means real unavailability for users.
For internal systems with low criticality, this maintenance window is usually acceptable. For systems that generate direct revenue or that need continuous availability, this downtime can represent a cost too high to be accepted.
How does zero-downtime migration work?
The core strategy for avoiding downtime is to keep both environments, the old and the new, running in parallel during the transition, with the data being continuously synchronized between them until the moment of the final switch.
For databases, continuous replication tools keep the target environment updated in real time with the changes made in the source environment, allowing the final switch to happen in seconds, not hours.
For applications, a common strategy is to run both versions simultaneously behind a load balancer, directing a small part of the traffic to the new environment first, validating that everything works correctly, and only then gradually migrating the rest of the traffic.
The role of DNS in the transition
Amazon Route 53 allows you to adjust the routing of traffic between the old and the new environment in a controlled way, with the possibility of quickly reverting to the original environment if any problem is identified during the transition, without impact to the end user.
Testing before the final switch
Before directing real traffic to the new environment, it is essential to validate that everything works as expected: performance, integrations, security, and the behavior of the application under real load. Skipping this step is one of the main reasons for problems during migrations that should be transparent to the user.
Not every migration needs to be zero downtime
Applying this strategy has an additional cost of planning and, in some cases, of duplicated infrastructure during the transition. For systems that tolerate a short maintenance window outside peak hours, a simpler migration may be sufficient. The decision depends on how much unavailability would cost the business during that window.
The result of well-done planning
With the right strategy, it is possible to migrate critical systems to AWS without end users noticing any interruption, protecting revenue and customer experience throughout the entire transition process.
CloudDog plans and executes migrations to AWS with strategies appropriate to the criticality level of each system, including zero-downtime migrations when necessary. Learn about our AWS Cloud Migration service and migrate your company without stopping the operation.
