# Build analytical, search, and vector projections

This recipe derives read models from an owned system of record without making
an index or warehouse authoritative for order mutations. The `.one` syntax is
illustrative end-product syntax.

## Declare projection obligations

```one
projection OrderSearch@1
    source parcelhub.orders#OrderPlaced@1
    source parcelhub.orders#OrderCancelled@1
    key OrderId
    fields [customer_id, order_id, status, searchable_text]
    freshness maximum 5s
    rebuild from retained_events
    deletion propagate_customer_erasure

projection OrderAnalytics@1
    source parcelhub.orders#OrderFact@1
    grain one_order_transition
    partition day
    freshness maximum 15m
    retention 7y
```

## Keep semantic and physical models separate

```text
Orders state -> authoritative mutation and exact current value
event log    -> retained transition input with causal references
search index -> lossy query projection, rebuildable
warehouse    -> analytical projection, delayed by contract
vector index -> similarity projection with declared model and quality evidence
```

## Query with freshness evidence

```rust,ignore
let result = search.orders(query).await?;
if result.freshness.age() > requirements.maximum_age {
    return ResourceState::Stale(result);
}
ResourceState::Ready(result)
```

Provider qualification proves declared recall/precision or consistency bounds,
not the marketing label “search”, “warehouse”, or “vector database”.

See [data-intensive systems](/one/guides/data-systems).