Europe 2026
Two Roads to Durable Agents: Replay vs. Snapshot — Eric Allam, CEO, Trigger.dev
Overview
This talk explores the fundamental shift required for AI agents in backend infrastructure, moving from stateless to stateful compute. It proposes two primary methods for achieving durable agents: replay and snapshotting. Replay, an evolution of traditional workflow engines, logs every interaction but can become unwieldy with complex agents. Snapshotting, a newer approach, preserves the entire execution state of a machine, offering a more robust solution for long-running, complex agent sessions.
Who should watch
- AI Engineers building and deploying agents.
- Product Managers defining agent capabilities.
- Developers seeking to create more reliable and resilient AI applications.
- Anyone interested in the evolution of backend infrastructure for AI.
- Those facing challenges with agent state management and error recovery.
Key takeaways
- Traditional backend architectures (CGI, LAMP, serverless) are stateless, relying on request + DB = response.
- Async tasks and multi-step workflows introduced the need for durable execution, leading to replay models in workflow engines.
- Agent loops, where the LLM orchestrates code, pose new challenges for durability, as replay logs can grow excessively large.
- Durable agents require two key components: durable context (append-only log of interactions) and durable execution state.
- Context durability can be achieved with existing technologies like databases or object storage.
- Execution durability is best handled by snapshotting and restoring the machine's state, preserving complex environments.
- Snapshotting techniques have evolved from process-level (CRIU) to micro-VMs (Firecracker), offering improved performance and compatibility.
- Optimized snapshotting, using techniques like seekable compression, can significantly reduce storage and network costs.
Notable quotes
*Agents are sort of forcing this move to become stateful compute.*
*The context is first and the most important, and it's just an append-only log of sort of everything that happened.*
*Instead of recreating the execution state from a log, we should use snapshot and restore.*
Unofficial community note. Prefer the recording for nuance.