SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42f3538e2ee8530a86c6159100ee978623585d816a9a6599b9d070916d290aff' 
  AND token = 'fJHowOgiu2s9jJooZ8EV7Y3qajl7ZHaHs/+aZz+qfB8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}