---
# nbd-oziy
title: Turso cache for list performance
status: completed
type: feature
priority: low
created_at: 2026-03-10T23:30:30Z
updated_at: 2026-03-10T23:30:30Z
---

Add a Turso (libsql) cache in `.nbd/cache.db` to accelerate `nbd list` and `nbd ready` for large ticket stores.

## Motivation

`list_tickets` currently does O(n) file reads on every call. For stores with hundreds of tickets this is measurably slow. A Turso/libsql cache avoids re-reading unchanged files by comparing file modification times (mtimes).

## Approach

### Runtime migration: async-std → tokio

libsql requires tokio. Migrate the entire crate:

- `Cargo.toml`: remove `async-std`, add `tokio = { version = "1", features = ["full"] }` and `libsql = "0.6"`
- `src/main.rs`: `#[async_std::main]` → `#[tokio::main]`, `async_std::fs::remove_file` → `tokio::fs::remove_file`
- `src/store.rs`: `use async_std::fs` → `use tokio::fs`, `use async_std::prelude::*` removed (tokio ReadDir uses `.next_entry().await` not stream iteration)
- `src/tests.rs`: `#[async_std::test]` → `#[tokio::test]`, `async_std::fs` → `tokio::fs`

### Crate dependency

```toml
tokio = { version = "1", features = ["full"] }
libsql = "0.6"
```

### store.rs additions

New async function `open_cache(root: &Path) -> Result<libsql::Connection>`:
- Opens (or creates) `.nbd/cache.db` via `libsql::Builder::new_local(path).build().await?.connect()`.
- Runs migration: `CREATE TABLE IF NOT EXISTS tickets (id TEXT PRIMARY KEY, json TEXT NOT NULL, mtime INTEGER NOT NULL)`.

New function `list_tickets_cached(root: &Path) -> Result<Vec<Ticket>>`:
1. Scan directory for files + mtimes (using tokio::fs::read_dir + metadata).
2. Open cache DB.
3. For each file: query cache for matching (id, mtime); if hit, deserialise from cached JSON; if miss, read file, parse, upsert to DB.
4. Delete DB rows for IDs no longer on disk.
5. Return sorted by priority desc.

Fall back to `list_tickets` on any cache error.

### main.rs

`cmd_list`, `cmd_ready`, `cmd_next` use `list_tickets_cached` instead of `list_tickets`.

## Files to change

| File | Change |
|---|---|
| `Cargo.toml` | Replace async-std with tokio, add libsql |
| `src/store.rs` | async_std → tokio fs API, add cache functions |
| `src/main.rs` | async_std → tokio main/fs |
| `src/tests.rs` | async_std → tokio test/fs |
| `tests/integration.rs` | Add cache smoke test |

## Validation

```sh
cargo fmt && cargo check && cargo clippy && cargo test
cargo run -- list  # should create .nbd/cache.db on first run
cargo run -- list  # second run uses cache
```