40-60% Cost Savings
Compared to Western European or North American developers
90%+ Satisfaction
Client satisfaction rates with Eastern European developers
6-8 Hours Overlap
Perfect time zone alignment with US East Coast
$2.3B Investment
Venture capital funding in Eastern Europe (2023)
AWS Cloud Migration: Lessons from Real Production Migrations
Last month, I watched our database replication lag spike to 2 hours during what should have been a "simple" RDS migration. The CFO was on a video call asking why the migration was taking so long. Our CTO was stress-testing our rollback plan. And I was SSH'd into a bastion host, frantically checking replication slots.
This is the reality of cloud migration that vendor whitepapers don't tell you about.
After migrating 30+ production applications to AWS (and learning from countless mistakes), here's what I wish someone had told me before my first migration.
Week 1: The False Start
Our first attempt at AWS migration failed spectacularly. Not because of AWS—because of us. We thought "lift and shift" meant we could just replicate our on-prem setup in the cloud. We were wrong.
Here's what actually happened:
1. Network Costs We Didn't Expect
We moved a monolithic app to EC2. Worked great! Until we got the bill. $12,000 in data transfer fees in the first month. Why? Our app made thousands of API calls between microservices we'd split up. Each call crossed availability zones.
The fix: VPC endpoints and keeping related services in the same AZ. Now data transfer costs: $400/month.
2. The Storage Migration That Wouldn't End
"Just rsync the files," they said. It took 3 weeks for 40TB to transfer over our 1Gbps line. By the time we finished, the source files had changed. We had to start over.
The real solution: AWS DataSync with bandwidth throttling during business hours. Completed the same migration in 6 days with minimal impact.
3. Security Groups Are Not Firewall Rules
Coming from traditional firewalls, we treated security groups the same way. Created one massive security group with 200+ rules. Then wondered why updates took 10 minutes to propagate.
Better approach: Targeted security groups per service. No more than 20-30 rules each. Use security group references instead of CIDR blocks everywhere.
The Database Migration That Almost Broke Us
Databases are where migrations get scary. You can't just copy-paste a production database and hope for the best.
Our PostgreSQL Migration Strategy
We had a 2TB PostgreSQL database serving 50,000 daily active users. Here's what worked (and what didn't):
What Failed:
- pg_dump during business hours - Locked tables, angry users, 2-hour outage
- Replication without testing - Replication broke silently, discovered it 3 days later
- Not monitoring replication lag - Nearly lost transactions during cutover
What Worked:
- AWS DMS with CDC (Change Data Capture) - Continuous replication with minimal lag
- Read replica cutover strategy - Promoted replica, minimal downtime
- Comprehensive rollback plan - Tested it 3 times before go-live
The actual cutover took 4 minutes. Planning took 6 weeks.
Infrastructure as Code or Bust
We tried to manage AWS resources through the console. Big mistake. After 2 months, nobody knew which resources were critical and which were test instances from last Tuesday.
Why IaC Saved Our Migration
Using Terraform changed everything:
- Version controlled infrastructure - Every change tracked in Git
- Reproducible environments - Dev, staging, prod identical
- Easy rollbacks - Just revert the commit
- Cost tracking - Tag everything automatically
A simple Terraform module we use for every EC2 instance:
module "app_server" {
source = "./modules/ec2"
name = "api-server"
instance_type = "t3.large"
ami_id = data.aws_ami.ubuntu.id
tags = {
Environment = var.environment
Application = var.app_name
CostCenter = "engineering"
}
}Now we can spin up entire environments in minutes, not days.
The Monitoring We Wished We Had
You don't realize how much your on-prem monitoring doesn't translate to cloud until your app is slow and you have no idea why.
What We Monitor Now
CloudWatch is good, but not enough:
- Application metrics - Custom metrics via CloudWatch agent
- Database performance - RDS Performance Insights
- Cost anomalies - AWS Cost Anomaly Detection
- Security - GuardDuty + Security Hub
- Distributed tracing - X-Ray for request flows
The game-changer? Setting up alerts BEFORE the migration. We caught 3 critical issues in staging that would have been disasters in production.
Real-World Migration Timeline
Forget the consultant estimates. Here's what actually happened with our migrations:
Small App (10 servers, 500GB data)
- Estimated: 2 weeks
- Actual: 5 weeks
- Why longer: Dependency mapping took 2 weeks we didn't plan for
Medium App (50 servers, 5TB data)
- Estimated: 8 weeks
- Actual: 14 weeks
- Why longer: Database migration required 3 attempts, security compliance review
Large Enterprise App (200+ servers, 20TB data)
- Estimated: 6 months
- Actual: 11 months
- Why longer: Legacy integrations, data quality issues, org politics
The Cost Optimization Nobody Talks About
AWS bills can spiral out of control fast. Here's what we learned about costs:
Month 1 After Migration
| Service | Expected Cost | Actual Cost | Why Different |
|---|---|---|---|
| EC2 | $5,000 | $8,500 | Forgot to stop dev instances |
| RDS | $2,000 | $2,100 | Pretty close! |
| Data Transfer | $500 | $12,000 | Cross-AZ traffic killed us |
| S3 | $200 | $300 | Lots of small files |
| Total | $7,700 | $22,900 | Ouch |
Month 6 (Optimized)
| Service | Cost | Savings Strategy |
|---|---|---|
| EC2 | $3,200 | Reserved instances, auto-scaling |
| RDS | $1,400 | Right-sized, reserved instance |
| Data Transfer | $400 | VPC endpoints, same-AZ design |
| S3 | $150 | Lifecycle policies, Intelligent-Tiering |
| Total | $5,150 | $17,750 monthly savings |
The Security Mistakes We Made (So You Don't Have To)
Security in the cloud is different. Here are our painful lessons:
1. IAM Policies Are Hard
First version: Gave developers AdministratorAccess. Seemed fine until someone accidentally deleted production S3 buckets.
Now: Least privilege everything. Use AWS managed policies where possible. Review permissions quarterly.
2. S3 Buckets Aren't Private by Default (Well, They Are, But...)
We misconfigured one bucket's policy during migration. It was public for 4 hours before our security scan caught it. Nothing leaked, but we almost made the news.
Now: Block public access at account level. Use bucket policies sparingly. Enable CloudTrail for everything.
3. Secrets in Environment Variables
We put database passwords in EC2 user data. Then wondered why Secrets Manager exists.
Now: All secrets in Secrets Manager or Parameter Store. Rotation enabled. No exceptions.
When Things Go Wrong: Our Rollback Story
Two months into production on AWS, RDS decided to have a bad day. Automated backup system failed. We needed to restore from snapshot. But which snapshot? They were all named "backup-YYYY-MM-DD" with no context.
Panic ensued.
We eventually found the right snapshot (after testing 3 wrong ones). Downtime: 6 hours. Customer trust: damaged. Lessons learned: invaluable.
Our Current Backup Strategy
- Automated snapshots: Every 6 hours with clear naming
- Cross-region replication: Critical databases replicated to 2nd region
- Regular restore tests: Monthly DR drills
- Documentation: Runbooks for every failure scenario
We test our backups monthly now. No exceptions.
The Tools That Actually Helped
Forget the AWS Migration Hub (sorry, AWS). Here's what actually made our migrations successful:
1. AWS Application Migration Service
Formerly CloudEndure. This tool saved us months. Continuous replication means you can test cutover multiple times without impacting production.
2. Terraform + Terragrunt
Managing infrastructure across multiple environments and regions. The learning curve is steep but worth it.
3. AWS Config + Custom Rules
Automatically flag any resource that doesn't meet our standards. Caught hundreds of compliance issues before audit.
4. Cost Explorer + Scheduled Reports
Weekly cost reports to every team. Suddenly developers care about rightsizing instances.
5. Systems Manager Session Manager
No more SSH keys or bastion hosts. Session Manager + IAM = secure, auditable access.
What I'd Do Differently
Looking back at 30+ migrations, here's what I'd change:
1. Start smaller. Don't migrate your most critical app first. Start with something low-risk.
2. Invest in training. Send your team to re:Invent. Get AWS certifications. The knowledge pays for itself.
3. Automate from day one. If you're clicking in the console, you're doing it wrong.
4. Budget 2x your estimate. For time AND money. Migrations always cost more than expected.
5. Document everything. Your future self will thank you during the 2 AM outage.
Final Thoughts
AWS migration isn't a destination—it's a journey. Our first migration was a disaster. Our tenth was smooth. Our thirtieth felt routine.
The difference? Experience, automation, and learning from mistakes.
Don't expect perfection. Expect problems. Plan for them. Build rollback strategies. Test religiously. And most importantly: learn from every migration.
Your first AWS migration will be hard. Your second will be easier. By your fifth, you'll wonder why you ever ran on-prem.
Have war stories from your own AWS migrations? Drop them in the comments. We all learn from each other's mistakes.
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