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Architecture

Rowsel has two components: a Flutter app and a Rust proxy. The proxy is the execution boundary between the device and the database.

Data flow

Section titled “Data flow”
 Device (Flutter)                Rust proxy                 Your database
 ─────────────────              ─────────────              ───────────────
 credentials in        ──HTTPS──▶  read-only policy   ──▶  PostgreSQL
 secure storage                    page-size limits        (direct, or via
 virtualized grid      ◀────────   statement timeout  ◀──   SSH bastion)
                                   error normalization
  1. The app sends the connection details and SQL to the proxy over HTTPS.
  2. The proxy opens a short-lived connection (or a pooled session), runs the statement under guardrails, and returns a normalized JSON response.
  3. Credentials are used only for the duration of the request or session — the proxy does not persist them.

The proxy

Section titled “The proxy”

Built in Rust with axum (HTTP), sqlx (PostgreSQL), russh (native SSH tunneling), and a SQL parser for statement classification. It is stateless for stateless requests, and keeps a small session registry for pooled connections and transactions.

Guardrails enforced at the proxy boundary:

  • Read-only classification — the query endpoint accepts a single statement classified as a read. Data-modifying CTEs, SELECT INTO, SELECT … FOR UPDATE, and multi-statement batches are rejected.
  • Read-only transaction — read queries run inside BEGIN READ ONLY with a SET LOCAL statement_timeout.
  • Enforced paging — user SQL is wrapped as a subquery to apply LIMIT/OFFSET, with a default page size of 200 and a maximum of 500.
  • Timeouts and body limits — default 10s / max 30s statement timeout, and a request body cap.

The app

Section titled “The app”

A Flutter app for mobile and tablet: secure on-device credential storage, a virtualized DataGrid, schema explorer, query editor, and local query history. The same proxy contract serves the app and any other client (for example a web tool calling the proxy from inside your network).

See the Proxy API reference for the full contract.