Migrating a Web Application to the Cloud: Plan, Risks, and Downtime

Moving to the cloud is not just a hosting change. It's a strategic step that changes the approach to scaling, security, and fault tolerance of a web application. However, migration without a clear plan and a well-thought-out cutover strategy can result in hours or even days of downtime, data loss, and user dissatisfaction. In this article, we will look at how to plan the migration of a web application to Yandex Cloud or AWS, minimize risks, and perform the switchover with virtually no downtime. If you need professional cloud solutions development, the ESK Solutions team is ready to handle all stages — from design to post-migration support.

Web Application Migration Plan to the Cloud: 7 Key Steps

Any successful migration starts with a detailed plan. Below is a step-by-step scheme proven on real projects.

Step 1. Audit of current infrastructure and application

Document the architecture: servers, databases, caches, message queues, external APIs, CI/CD pipelines. Assess peak loads, storage volumes, latency requirements. Example: For an online store with a peak RPS of 5000 and a database size of 200 GB, it is worth choosing cloud services with a fast IOPS disk.

Step 2. Selection of cloud provider and target architecture

At this stage, the capabilities of Yandex Cloud and AWS are compared. Criteria: availability of necessary services (managed Kubernetes, serverless functions, object storage), cost, data center location, compliance (152-FZ, GDPR). The choice often comes down to Yandex Cloud if data must remain in Russia, or AWS for global reach. If needed, our specialists help with web application development taking into account the cloud architecture.

Step 3. Data preparation and synchronization

Setting up database replication, migrating file storage, synchronizing states. For relational databases, logical replication or dumps followed by apply at cutover time are used. For NoSQL, either native tools or custom scripts.

Step 4. Deploying the target environment

Infrastructure as code (Terraform, Pulumi) allows you to spin up an identical environment in the cloud in hours. Don't forget about network configuration, security groups, IAM roles, SSL certificates.

Step 5. Comprehensive testing

This stage includes load testing, functional checks, and fault tolerance testing. It is important to run regression scenarios and ensure external integrations work correctly. At ESK Solutions, we use automated test suites for SaaS solutions, as described in the SaaS application development section.

Step 6. Cutover strategy and traffic switching

Cutover is the key moment of migration when production load is moved to the new environment. We'll discuss it in detail in a separate section.

Step 7. Post-migration monitoring and optimization

After the switchover, metrics are monitored for several days: response time, error rate, resource consumption. If necessary, autoscaling is adjusted, alerts are configured, and cost optimization is performed.

Risks of Migration to the Cloud and Ways to Minimize Them

Migration is a project with a high degree of uncertainty. The main risks and methods to mitigate them:

• Downtime. The most dangerous risk. Reduced by proper cutover and preliminary data synchronization.
• Data loss. Occurs due to incomplete synchronization or errors in migration scripts. Solution: full backups, incremental synchronization, and checksum verification.
• Software version incompatibility. Different versions of OS, DBMS, or dependencies may be used in the cloud. Avoided through containerization (Docker) and IaC.
• Performance issues. Different disk subsystem, network latency. Load testing on the target environment is mandatory.
• Security and compliance breaches. Requires proper configuration of encryption, access controls, and regulatory compliance.

A professional team can not only assess risks but also propose an optimal architecture. This is often sought when it comes to CRM development or corporate portals with sensitive data.

Cutover Strategy: How to Minimize Downtime

Cutover is the process of switching production traffic from the current infrastructure to the cloud. The main goal is to reduce downtime to zero or just a few seconds. Let's look at the main approaches.

One-Time Cutover (Big Bang)

This is suitable for applications where a short interruption is acceptable (e.g., overnight). You stop writing to the old database, run a final sync, change the DNS record, and redirect traffic to the cloud. Downtime equals the duration of the sync plus the DNS TTL. You can shorten it by lowering the TTL to 60 seconds beforehand. Example: For a service with 100,000 monthly users, a nighttime cutover was completed with just 2 minutes of downtime.

Gradual Switchover (Canary/Blue-Green)

This approach eliminates downtime entirely. For instance, in AWS, using Route 53 with weighted routing, you direct 5% of traffic to the new cloud, monitor for errors, then increase the share to 100%. In Yandex Cloud, you can similarly use an Application Load Balancer with virtual machine groups. This method requires real-time database synchronization (e.g., via replication).

DNS Switching and Weighted Distribution

A classic method is changing the CNAME record to switch to the cloud's elastic IP. The downside: DNS propagation delays. It's better to combine with an Anycast network or CDN, where backend changes happen instantly.

The ESK Solutions team specializes in seamless web application migrations. We design a cutover scenario individually, taking into account the architecture and business requirements. Learn more about cloud services and infrastructure.

Yandex Cloud vs AWS for Web Application Migration

The choice between these platforms depends on many factors. Let's compare the key aspects.

Geographic Availability and Latency

AWS has regions worldwide, which is convenient for global projects. Yandex Cloud offers three zones in Russia and one in Kazakhstan, with excellent latency for Russia and the CIS.

Managed Services

Both platforms cover the main needs: Kubernetes, serverless, managed databases. AWS leads in the number of services; Yandex Cloud excels in integration with Russian services (Yandex SpeechKit, Yandex Object Storage).

Cost

Yandex Cloud is often cheaper for workloads within Russia, especially given currency fluctuations. AWS may be more advantageous with reserved instances and grants.

Compliance and Localization

For personal data of Russian citizens, Yandex Cloud provides certified segments and compliance with 152-FZ. AWS is more complex in this regard, but a hybrid architecture is possible.

We perform accurate calculations and make informed choices as part of our cloud infrastructure development service — from strategy to launch.

Frequently Asked Questions

How long does a web application migration to the cloud take?

The duration depends on the application's complexity, data volume, and chosen strategy. A simple project can be migrated in 2-4 weeks, while a complex one with a microservices architecture can take 2 to 6 months. Synchronizing large databases is often the bottleneck.

Can downtime be completely avoided during migration?

Yes, by using blue-green or canary strategies with synchronous data replication. However, this requires more complex preparation and may increase the budget, so it's chosen for systems that are critical to uptime.

What are the most common mistakes when migrating to the cloud?

Main mistakes: insufficient testing under real load, ignoring auxiliary services (queues, caches), lack of a rollback plan, incorrect estimation of cloud resource costs, and overlooked dependencies on on-premise infrastructure.

Do I need to modify the application code when moving to the cloud?

Generally, with containerization and a 12-factor approach, the code remains untouched. However, changes may be needed in configurations (environment variables, service endpoints). Sometimes database queries are optimized if the cloud DBMS has different settings.

If you have any further questions or need a custom migration plan, simply contact us — we'll help you develop an effective cloud transition strategy.