Payment Migration & Integration
Migrating Millions in Recurring Revenue with Zero Downtime
Babbel
Millions
Subscriptions Migrated
Zero
Downtime
100%
Revenue Protected
The Challenge
Babbel, a leading language-learning platform with millions of subscribers globally, needed to migrate their entire recurring billing infrastructure from Adyen to Stripe. This was a business-critical project requiring:
•Migration of millions of live subscriptions without any revenue disruption
•Support for multiple payment methods across global markets (credit cards, PayPal, SEPA)
•Zero-downtime execution with complete auditability
•Deep coordination across engineering, product, finance, and data teams
•Fault-tolerant architecture for high-stakes billing operations
Our Solution
Andrej was brought on as lead engineer and payment migration consultant to architect and execute this complex migration. Our approach:
Technical Architecture
Designed and implemented Stripe Billing flows including Setup Intents, payment method Mandates, and multi-method support
Built test-covered, idempotent background jobs using Rails and DelayedJob, scheduled via AWS EventBridge Scheduler
Developed modular service objects and orchestrators with custom error handling for retries, rate limits, and API anomalies
Created comprehensive verification and reporting pipelines
System Integration
Integrated with multiple internal systems via HTTP, Lambda triggers, webhooks, and event buses
Ensured consistent data flow and status propagation across decoupled systems
Deployed and monitored infrastructure using Terraform and AWS at scale
Process & Leadership
Drove sprint planning and authored detailed technical specifications
Conducted code reviews and oversaw verification pipelines to ensure migration integrity
Acted as both lead implementer and strategic advisor, shaping architectural decisions and rollout sequencing
Managed edge-case strategy and supported internal alignment around billing risk
Results & Impact
Successfully migrated millions of live subscriptions with zero revenue loss
Zero downtime throughout the entire migration process
Complete auditability and reconciliation of all payment data
Fault-tolerant architecture handling API failures and edge cases gracefully
Seamless support across multiple global markets and payment methods
Reduced billing infrastructure complexity and improved maintainability
Project Details
Client
Babbel
Industry
EdTech / Language Learning
Project Type
Payment Migration & Integration
Timeline
November 2024 - Present
Technologies
Ruby on RailsStripe BillingAWS EventBridgeDelayedJobTerraformAWS LambdaPostgreSQLWebhooks
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