Scaling Event-Driven Systems with Temporal: Signals, Cassandra & Production Lessons from Fwdays Tech Talks

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Scaling Event-Driven Systems with Temporal: Signals, Cassandra & Production Lessons

1 hour 12 minutes Posted Feb 13, 2026 at 2:51 pm.

Intro

What is Day.io and what problems does it solve?

Legacy architecture: where did the system start, and what pain points emerged over time?

Why Temporal and what alternatives were considered?

Real-world workflows: what business processes are modeled as Temporal workflows?

Observability and debugging: how Temporal UI and metrics help in production

System architecture overview: how events flow from microservices into workflows

Signals vs activities: how the workflow design evolved in practice

V1: 100% CPU and the domino effect

V2: Signals as a performance breakthrough

Why tuning alone wasn’t enough?

V3: Merging activities for 5–7x scalability

Temporal at scale: reducing pressure on the cluster

Postgres vs Cassandra for Temporal persistence

Lessons learned from running Cassandra in production

Reliability under load and avoiding risky shortcuts

Real-world Temporal use cases beyond metrics

Using signals for async workflows and external integrations

Migrating customers without a big-bang release

When Temporal is the right tool?

What the team wishes they knew before starting?

Final advice and recommendations

Don’t forget to subscribe and like!

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Show notes

Welcome to the 4 episode of Architecture Deep Dive with Oleksii Petrov!

In today’s podcast, our guest — Andriy Lupa, Tech Lead at Day.io, shares how their team rebuilt a high-load, event-driven system serving the Brazilian market and processing millions of punch events daily. We dive into the legacy pain points, the architectural shift to Kafka and Temporal, and how signals and workflow design changed their scaling strategy. Andriy walks us through the journey from 100% CPU and cascading failures to 5-7× scalability, including the move from Postgres to Cassandra and the real trade-offs behind it. We also discuss durable timers, safe cron jobs, migration with feature flags, versioning challenges, and when Temporal is and isn’t the right tool.

Link to Andriy’s talk: "Scaling in space and time with Temporal" 🔗 https://youtu.be/jxHVcGbwZWM

What you should subscribe to:

– More interesting content for developers: https://fwdays.com/en/events

– Fwdays Twitter: https://twitter.com/fwdays

– Oleksii Petrov's Telegram channel: https://t.me/OleksiiTheArchitect

– Oleksii Petrov's LinkedIn: https://www.linkedin.com/in/alexhelkar/

– Andriy Lupa's LinkedIn: https://www.linkedin.com/in/andriy-lupa?utm_source=share_via&utm_content=profile&utm_medium=member_android

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