HomeCase StudiesFinTech Migration
Success Story

Scaling to 5M+ Users via Event-Driven Architecture.

How Coretus migrated a Series-B NeoBank's legacy Node.js monolith to AWS Microservices, eliminating 4-hour daily outages and reducing latency by 90%.

Timeline
8 Months
Model
Managed Squad
Key OutcomesVerified Data
90%
Faster API Response
400ms
$12k
Monthly Savings
$45k Spend
0
Downtime Events
Daily Crashes

Executive Summary

The client was facing severe scalability issues with their legacy Node.js monolith during peak trading hours.

Coretus deployed a specialized "Modernization Squad" to implement the Strangler Fig pattern, gradually decoupling core services (Auth, Ledger, Notifications) into an Event-Driven Architecture on AWS, resulting in zero downtime during their record-breaking IPO launch.

Primary Objective
Eliminate database locks and reduce AWS OpEx without pausing feature development.

The "Success Disaster"

The Monolith Bottleneck

A single Node.js instance was handling Auth, Ledger, and Notifications. During the "2 PM Transaction Rush," CPU spikes caused cascading failures, locking the entire database.

Financial Bleed

To keep the site up, the internal team vertically scaled AWS instances to maximum capacity 24/7. This resulted in a $45k/month bill for traffic that only spiked for 2 hours a day.

The Unit We Deployed

We injected a self-managed "Modernization Squad" to work alongside the client's feature team.

Tech Lead
Architect
2x Backend
Golang
1x Frontend
React
1x DevOps
Terraform

From Monolith to Mesh

BEFORE

The Bottleneck

Shared DB: Single point of failure. One heavy query kills the app.
Vertical Scale: Costly EC2 instances running 24/7.
AFTER

The Mesh

Event Driven: Kafka decouples services. No blocking calls.
Serverless Scale: AWS Lambda scales to zero when idle.
Speed Advantage

We Didn't Start From Scratch.

Migrating authentication and payment logic is risky and slow. We skipped the boilerplate by injecting Coretus Microservice Accelerators—pre-audited, SOC2-compliant code modules.

Auth Core Module
Saved 3 Weeks Dev Time
Payment Wrapper
Saved 4 Weeks Dev Time

Time to Market Impact

Standard Agency6 Months
Coretus (With Accelerators)3.5 Months

The "Strangler Fig" Roadmap

Month 1-2: Stabilization

Codebase SAST audit. Implemented Redis caching to stop the database bleeding immediately.

Month 3-5: The Decoupling

Extracted "User Service" and "Ledger" into Golang. Routed 10% of traffic via API Gateway.

Month 6-8: Optimization

Migrated 100% of traffic. Decommissioned Node.js monolith. Final Handover.

Governance & Quality

  • Daily Standups (10:00 AM)
  • Weekly Sprint Demos
  • Slack Connect Channel
  • Bi-Weekly Code Reviews

The Bottom Line

Financial Impact
$12k / mo
Reduction in Cloud Spend
Performance
45ms
Avg API Response (down from 400ms)
Stability
99.99%
Uptime during Black Friday

"The Coretus squad didn't act like vendors. They pushed back on bad architectural decisions, brought their own accelerators, and owned the outcome. They saved our Series B launch."

VP Engineering
UK FinTech Unicorn

Technologies Deployed

Lambda
Go
K8s
PostgreSQL

Similar Success Stories

HealthTech

Building a SOC2 Compliant Data Lake

How we secured patient data for a Telehealth giant.

100% Audit Success
Logistics

AI Route Optimization

Reducing fuel costs by 22% via ML models.

22% OpEx Saved
Facing Scalability Issues?

Don't Let Tech Debt Kill Your Growth.

If your monolith is crashing at 2pm, we can fix it. Book a free 30-minute architecture review with the Lead Architect from this project.