45% infrastructure cost reduction through a strategic AWS migration

The context

FinTech Solutions operates a payment processing platform handling $500 million in annual transactions. Their aging on-premise infrastructure had become a strategic drag: $840,000 in annual costs, availability of only 98.5%, two-week deployment cycles and recurring outages under peak load.

With transaction volume expected to double and international expansion planned, the status quo was no longer sustainable.

Our approach

We designed a complete migration strategy following AWS best practices, with one absolute requirement: zero service interruption.

Phase 1 — Audit and planning (Weeks 1-2)

A full inventory of the existing infrastructure revealed widespread under-utilization: 12 physical servers at 35% average load, SAN storage used at 45% and oversized databases. AWS cost modeling projected a 56% reduction in the first year.

Workloads were classified under three strategies: rehost (60%), replatform through containerization (30%) and refactor of the critical paths (10%).

Phase 2 — Cloud foundations (Weeks 3-4)

The entire infrastructure was defined as Infrastructure as Code with Terraform: multi-AZ VPC, EKS cluster, RDS databases with encryption, replication and automated backups.

Security and compliance were built in from the start: encryption with KMS, logging with CloudTrail, threat detection with GuardDuty, and compliance monitoring with AWS Config — all codified and reproducible.

Phase 3 — Application migration (Weeks 5-8)

Applications were containerized with Docker and deployed on Kubernetes (EKS) with auto-scaling, health checks and zero-downtime rolling updates.

The database migration — the most critical step — was carried out with AWS DMS (Database Migration Service) in continuous replication mode. The final cutover took place only after confirming that replication lag was under one second.

Phase 4 — Traffic cutover (Weeks 9-10)

Traffic was shifted progressively via Route 53 (weighted routing): 10% → 25% → 50% → 75% → 100%, each step validated before moving to the next, with instant rollback available at all times.

Phase 5 — Optimization (Weeks 11-12)

After the migration was complete, we optimized costs through right-sizing based on real CloudWatch metrics, Spot instances for non-critical workloads (-70%), reserved instances for the baseline load (-40%), and S3 lifecycle policies for automatic archiving.

Results

Cost reduction — From $840,000 to $384,000 annually, a 45% direct saving. Including the elimination of 2 ops positions and productivity gains: $696,000 in total savings.

Item	On-premise	AWS	Savings
Compute	$420K	$162K	61%
Database	$180K	$144K	20%
Storage	$120K	$36K	70%
Network	$60K	$42K	30%
Data center	$60K	$0	100%

Performance — API response time: 450 ms → 180 ms. Page load: 3.2 s → 1.1 s. Zero outages on Black Friday (versus crashes every previous year).

Reliability — Availability up from 98.5% to 99.99%. Recovery time reduced from 4 hours to 15 minutes.

Delivery velocity — Deployment frequency: from every 2 weeks to 10 times per day. Deployment duration: from 4 hours to 8 minutes. Rollback: from 2 hours to 30 seconds.

Compliance — SOC 2 Type II certification obtained. PCI-DSS compliance maintained with 80% of controls automated.

The infrastructure went from a liability to a competitive advantage. The engineering team regained its capacity to innovate.

Lessons learned

1. Lay solid foundations — A well-architected VPC and native security from day one prevent costly rework
2. Automate everything — Infrastructure as Code is not optional, it is a prerequisite
3. Migrate progressively — Weighted routing enables instant rollback and reduces risk at every step
4. Measure continuously — Right-sizing based on actual usage is a permanent optimization lever
5. Compliance as code — Automating compliance controls reduces workload and increases reliability