SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0509ffc78c36eeab96bbfaa8a3343bf7d387227feceddddaaf23d4a126281af2' 
  AND token = '/4yAPbkw/Fwabw7Qk8aF+RQ8DN+bRRLBIzYi/HWDtAM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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