CONCEPT Cited by 1 source

SQLSTATE 53000 Traffic Control error¶

SQLSTATE 53000 is the Postgres error class (insufficient_resources) that PlanetScale Traffic Control raises when a query in Enforce mode exceeds its budget. The error message is prefixed with the string [PGINSIGHTS] Traffic Control: — a machine-readable discriminator that lets callers distinguish Traffic Control rejections from all other resource- class errors Postgres emits under the same SQLSTATE (out-of-memory, disk-full, etc.).

Shape¶

On the wire, an Enforce-mode block arrives as a standard Postgres ErrorResponse frame with severity ERROR, SQLSTATE 53000, and a message like:

[PGINSIGHTS] Traffic Control: query exceeded budget
'free-tier-export' (cpu share 20%)

Drivers surface it as their usual error type — in pgx/v5, a *pgconn.PgError unwrappable via errors.As:

const sqlstateTrafficControl = "53000"

func isTrafficControlError(err error) bool {
    var pgErr *pgconn.PgError
    return errors.As(err, &pgErr) && pgErr.Code == sqlstateTrafficControl
}

The [PGINSIGHTS] Traffic Control: prefix check is optional but recommended — SQLSTATE 53000 alone covers legitimate resource- exhaustion errors from which retry is unlikely to help.

Why a standard SQLSTATE, not a bespoke one¶

Traffic Control is an extension running inside Postgres. Extensions can raise any SQLSTATE they want but reusing a standard class (53000 = insufficient_resources) keeps the error compatible with pre-existing error-handling code paths:

Callers that already catch 53xxx for memory-pressure / disk- pressure get Traffic Control handling for free.
Libraries and ORMs that map SQLSTATE to typed exceptions don't need updates.
Log-aggregation pipelines bucketing by SQLSTATE class surface Traffic Control events alongside other resource events.

The prefix string is the extension's way of adding its own discriminator without breaking the standard-class contract.

Caller response semantics¶

The right response depends on the query's role in the application, not on the error class:

Non-critical (analytics, reporting, exports) → return 503 Service Unavailable to the caller, or serve a cached / stale result. "That's exactly the controlled failure mode Traffic Control is designed to create" — the point of Enforce mode is to make the load go away, not to make it retry harder.
Critical paths (auth, checkout, core read) → short retry with exponential backoff (100ms → 200ms → 400ms over 3 attempts). The spike may clear in hundreds of milliseconds; failing a critical query propagates the degradation to the user unnecessarily.

Canonical retry helper shape (Source: sources/2026-04-21-planetscale-patterns-for-postgres-traffic-control):

for attempt := range maxRetries {
    rows, err := db.QueryContext(ctx, query, args...)
    if err == nil { return rows, nil }
    if !isTrafficControlError(err) || attempt == maxRetries-1 {
        return nil, err
    }
    select {
    case <-time.After(backoff):
        backoff *= 2
    case <-ctx.Done():
        return nil, ctx.Err()
    }
}

Two escape predicates matter: non-Traffic-Control error short-circuits immediately (don't retry a syntax error), and ctx.Done() short-circuits retry (request-timeout budget wins over retry budget).

Operational pairing with Warn mode¶

Budget authors don't flip budgets directly to Enforce. The canonical operational lifecycle is Warn mode → Enforce mode: observe which queries would be blocked via the Postgres notice channel first, tune the threshold on real traffic, then switch to Enforce. By the time SQLSTATE 53000 starts flowing, the fire-rate has been characterised.

Not the only SQLSTATE `53000` source¶

Unextended Postgres also raises 53000 for genuine hardware / kernel resource exhaustion (out of shared memory, out of file descriptors, etc.). The [PGINSIGHTS] Traffic Control: prefix is how callers distinguish. Without the prefix check, retry-on-53000 might retry a legitimately-overloaded database and make the problem worse.

Seen in¶

sources/2026-04-21-planetscale-patterns-for-postgres-traffic-control — canonical wiki introduction. Josh Brown canonicalises the SQLSTATE + prefix + pgx/v5 detection helper + role-dependent caller response (503 vs retry-with-backoff).