Here’s the outline for the slides and what will be shown in the presentation:

Intro about me and the talk (1-3 slides)

The problem

• A/B testing
  • What is A/B testing in principle
• Architecture of the system
  • The previous solution at the organization
• Previous (slow & heavy) solution
  • Why the previous solution motivated us to look for an alternative
• Future (fast & lean) solution
  • New solution involving Edge Computing

The solution (happy path) V1

• Cloudflare Worker
  • Cloudflare Edge network and their Workers
• A/B test decision made in the cloud and stored in the header
  • Using 3rd party tool for A/B testing and how the decision happens in the cloud near the end user
• Origin (backend)
  • What serves are listening and expecting A/B decision
• Edge Cache
  • We had to have everything CDN cached properly
• Testing everything
  • How to test the whole system and services that they are working
  • A tool called Artillery for high load testing

The solution (when things go left) V2

• What happens if 3rd party A/B testing service is down?
  • We need to store events and resubmit when the service goes online
  • How to store events?
• Options for storing user events - KV, Durable Objects, Kafka, Amazon SQS
• Durable Objects
  • A feature from Cloudflare that introduces distributed computing/programming
• Emptying the queue from Durable Object
• Distributed Computing with Durable Object Groups
• Testing everything (again)
  • How we simulated 1000 req/s from our machines

The solution (common sense) V1.1

• Cloudflare Worker does the main job
• If 3rd party service is down, save events to Durable Object and retry later
• Reestimate the cost of such fault tolerant system and put a limit on how tolerant it is
• Backup plan for future development

Takeaways

• Speed and Scalability on Edge
• Fault tolerance and where to put a limit - figure out what you are building and for who, talk to management and people responsible for business decisions
• Have a backup plan
• Feel free to experiment
• Advocate for common sense (even if it does not appear as common)