Dan Harper and his teams at Xero just wrapped up big changes within the business. With involvement required from 40+ teams, changes to many critical legacy systems and the need to build several new platforms, they carried massive risks throughout the project and particularly when "going live" to customers. In this talk, Dan will share the learnings on what worked, what didn't work and the continuous delivery practices they implemented that helped the team reduce risks and incrementally deliver changes to production across global regions and different customer segments.

1. with Continuous Delivery
Delivering big change with high reliability
Reducing Risk

2. The Challenge
High Complexity
Low Knowledge
Low Confidence
Zero Downtime

3. The Hypothesis

4. The
Starting Point

5. Hire Champions

6. Hire Champions
V

7. Building
Culture

8. Core Values & Practices
Repeatability
Simplicity
Fast Feedback
Clean Code
Pair
Programming
Automate
Repetitive Tasks
Refactoring
Test Driven
Design
Continuous
Integration
Vertical Slices
Simple
Design
Collective Code
Ownership
https://www.thoughtworks.com/insights/blog/what-are-our-core-values-and-practices-building-software

9. Fast Feedback through CI
Pre-Check-In
Unit Tests
Integration Tests
Commit/Push
CI
Unit Tests
Integration Tests
Deploy to
Production
● 100% containerised environment
● Optimised for fast feedback
● Pre-Check-In and CI pipeline are the
same script
● Everything post commit is automated

10. Tracking Metrics
Small, fast,
incremental changes
Deployment
Frequency
20x /day
Delivery Lead
Time
12 mins From Developer
Commit to
Production
Release

11. Cycle Time
Current Cycle
Time
4 days
Kickoff Deployment
Target Cycle
Time
1 day

12. Working with
other teams

13. Reducing Dependencies
Delays push out
dependencies
Big releases have a
high risk of failure

14. Continuous Delivery at Scale

15. Contract Driven Development

16. Communication Breakdown!
What is a
“Feature”?
Who owns
this?
What
domain?

17. Feature Flag
Everything!

18. Customer Segmentation
Global Region New/Existing Free Trial Source

19. Functional Slices
Xero.com
Channels
Migration
Demo
Trial
Learn
Partner
Mobile
Navigation
Monolith
Invoices
Bank Feeds
Bills
Quotes
Payroll
Monolith
Mobile
Navigation
Microservices
Invoices
Bank Feeds
Bills
Quotes

20. Validating in Production
● Region: Australia
● New Customer
● Free Trial
● Source: Partner

21. Fastest Path to Go Live
● Region: Australia
● New Customer
● Free Trial
● Source: Partner
Start
Live in Production!

22. Architectural Approach
Upstream
Systems
Downstream
Systems
Domain
API
Adapters Internal
Domain
Async via
Queues

23. The
Outcome?

24. Success!

25. Reflections

26. Huge Wins
● Decoupled Architecture
● Feature Flagging
● Going Live Early and Often

27. Improvements for Next Time
● Go slow at the start
● Teach the “why” more
● Over-communicate!