SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3e5f79348215901b86227549717d16db233311127346918f0f0d7e26074e1daf' 
  AND token = 'Ks8q+rFLgyWKvPWjxte8SsFLw9WyGRgpUH1CbY9NIOI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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