SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b740ccbecde7735fd73b0bcdc557fdb6c7b9e269566bf390d53024c6543f847' 
  AND token = 'J4l8jAaE4QnKvHIFd5t1iQRjyY/nsF2IFahbSni6Yh4=' 
  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"
    }
  }
}