adr

Architecture Decision Records

This directory records architecturally significant decisions for Verdigris — the choices that shape the system and would be expensive to reverse. Each ADR captures the context, the decision, and its consequences at a point in time.

We follow the lightweight ADR convention (Michael Nygard's format). An ADR is immutable once Accepted: if a later decision changes it, add a new ADR that supersedes it rather than editing history.

Index

ADR	Title	Status
0001	Deterministic Simulation Testing as a core constraint (and DataFusion over DuckDB)	Accepted
0002	JSON manifest as an Apache Iceberg stand-in	Accepted
0003	Split ingest (writer) from query (readers) for single-writer safety	Accepted

ADR-0001 lives at ../dst-architecture.md for historical reasons (it predates this directory) and is the canonical record for both the DST methodology and the DataFusion-not-DuckDB engine choice.

Writing a new ADR

1. Copy the format below into NNNN-short-title.md (zero-padded, next number).
2. Fill in Context → Decision → Consequences. Be honest about trade-offs and about what is assumed but unproven.
3. Set Status: Proposed, open a PR, and move it to Accepted (or Rejected) on merge.
4. Add a row to the index above.

# ADR-NNNN: <title>

**Status:** Proposed | Accepted | Rejected | Superseded by ADR-XXXX
**Date:** YYYY-MM-DD

## Context
What forces are at play — technical, product, operational.

## Decision
What we are doing, stated plainly.

## Consequences
What becomes easier, what becomes harder, what we now owe.