SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c35c63aacf8f4ac29dad17fe38bf7de9d72d41b9e70777c1e5697b63a2fbcc8b' 
  AND token = 'KLZyf1TpW0Bh+RMUv4WRWUYaZ+Jp+4XZP0IoWqv9/Xk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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