# Timeline

> Unified event timeline service with HLC-ordered queries, critical path analysis, and deterministic replay.

## Purpose

Timeline is the query and presentation layer for cross-service event correlation and auditing. It provides Hybrid Logical Clock (HLC)-ordered event queries, critical path analysis for latency diagnosis, and deterministic replay capabilities. Timeline reads events that have been indexed by the separate TimelineIndexer module, serving as the read-side of the event timeline infrastructure.

## Quick Links

- [Architecture](./architecture.md)

## Status

| Attribute    | Value              |
|-------------|---------------------|
| **Maturity** | Production          |
| **Source**   | `src/Timeline/`     |

## Key Features

- HLC-based causal event ordering
- Correlation ID queries
- Critical path analysis (latency stages)
- Service-filtered timeline views
- Event export and deterministic replay

## Dependencies

### Upstream

- Eventing infrastructure (StellaOps.Eventing) - event storage and indexing
- HybridLogicalClock library - causal timestamp generation and comparison

### Downstream

- Platform - timeline views for operator dashboards
- CLI - event query commands
- Web - timeline UI components
- Replay - deterministic replay of event sequences

> **Note:** Timeline is the query/presentation service. TimelineIndexer (separate module) handles event ingestion and indexing. They are independently deployable services.