Email and voice for your agent.

def accept(path, key, event):
    with connect(path) as db:
        db.execute('BEGIN IMMEDIATE')
        existing = db.execute(
            'SELECT event_id FROM jobs WHERE delivery_key=?', (key,)
        ).fetchone()
        if existing:
            return 204 if existing['event_id'] == event['event_id'] else 409
        db.execute(
            'INSERT INTO jobs(delivery_key,event_id,body) VALUES (?,?,?)',
            (key, event['event_id'], json.dumps(event))
        )
    # SQLite committed before the HTTP acknowledgement.
    return 204