SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2a666a12f758c7ece1271746af79b2020b592704f4476e483497caa656a50f44' 
  AND token = 'h9Q7R27Tz+FmlJGqhqhFLPa2X3BmywxokltYZ3IGUKA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}