SaaSEurope16 months

SaaS Platform - Europe

Migrating a Legacy Monolith to Microservices with 90% Faster Deployments

European B2B SaaS Company
2022
SaaS Platform - Europe

Overview

A European B2B SaaS company growing from 50 to 200 employees was crippled by a legacy monolithic codebase. Deployments took days, teams blocked each other, and outages were frequent. The business needed a modern engineering foundation to sustain its growth trajectory.

The Challenge

The monolith had accumulated years of technical debt. Deployments required full regression testing and manual steps taking 2-3 days. Any team's change could break another team's feature. Infrastructure was manually provisioned, monitoring was minimal, and on-call engineers were burning out from constant incidents.

Key Pain Points

2-3 day deployment cycle blocking product velocity
Teams constantly breaking each other's features
Manual infrastructure provisioning taking days per environment
No automated testing — all regression testing was manual
Minimal observability making incident diagnosis very slow
Engineers burning out from frequent on-call incidents

The Solution

Led a 16-month strangler-fig migration to microservices, introduced infrastructure as code, built a full CI/CD platform, established SRE practices, and rebuilt the engineering culture around DevOps principles.

1

Phase 1: Stabilisation & Observability (Months 1-3)

  • Deployed Prometheus and Grafana for full-stack observability
  • Established on-call runbooks and incident playbooks
  • Introduced feature flags to de-risk deployments immediately
  • Began automated test suite covering critical paths
  • Mapped service boundaries within the monolith
2

Phase 2: CI/CD & Infrastructure as Code (Months 4-7)

  • Built Jenkins CI/CD pipelines for automated test and deploy
  • Provisioned all infrastructure via Terraform
  • Containerised the monolith with Docker for environment parity
  • Set up Kubernetes cluster for microservice hosting
  • Reduced deployment time from 3 days to 4 hours
3

Phase 3: Microservices Migration (Months 8-13)

  • Extracted billing, notifications, and auth as independent services
  • Implemented API gateway for service routing
  • Built event-driven communication between services via Kafka
  • Established team ownership model — one team per service
  • Achieved zero-downtime deployments for all extracted services
4

Phase 4: Culture & Full Migration (Months 14-16)

  • Completed migration of remaining monolith domains
  • Established error budgets and SLOs per service
  • Ran DevOps culture workshops across all engineering teams
  • Built internal developer portal for service discovery
  • Reduced deployment frequency from weekly to multiple times daily

Technologies Used

Kubernetes
Container Orchestration
Docker
Containerisation
Jenkins
CI/CD Pipelines
Prometheus
Metrics & Alerting
Grafana
Observability Dashboards
Terraform
Infrastructure as Code
Kafka
Event-Driven Messaging
Vault
Secrets Management

Results & Impact

Deployment Speed
90%
Faster — from 3 days to 20 minutes
System Uptime
99.95%
Up from 97.8% pre-migration
Infrastructure Cost
-50%
Through right-sizing and IaC
Team Productivity
3x
Feature delivery velocity increase
Deployment Frequency
10x
Multiple deploys per day achieved
Incident MTTR
-75%
Mean time to resolution

Business Impact

Engineering attrition dropped to zero in the 12 months post-migration
Time-to-market for new features reduced from months to weeks
Successfully onboarded 5 enterprise clients requiring SLA guarantees
Raised €25M Series B on the strength of technical due diligence
Platform scaled from 500 to 5,000 business customers
Won Best Engineering Team award at European SaaS Summit 2023

The transformation was more than technical. Our engineers are proud of what they build again. We deploy dozens of times a day, incidents are rare, and we can finally keep our product promises to customers.

CTO
European B2B SaaS Company

Project Highlights

CI/CD pipeline and deployment dashboard

CI/CD pipeline and deployment dashboard

Microservices architecture overview

Microservices architecture overview

Observability and SLO tracking

Observability and SLO tracking

Key Takeaways

Strangler-fig migration avoids big-bang rewrites and reduces business risk
Observability must be established before migration to diagnose issues fast
Feature flags decouple deployment from release, enabling safer velocity
Team ownership models aligned to service boundaries unlock parallel delivery
Infrastructure as code is foundational to any scalable DevOps practice
Cultural change is as important as technical change in DevOps transformations

Ready for Similar Results?

Let's discuss how fractional CTO services can help your startup achieve remarkable growth and technical excellence.

Book Free ConsultationView More Case Studies