SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '52a4a0b3efbf7b78d715ff10d0a0697855adceacb1f342a9fd3da2d142a8bc6b' 
  AND token = 'tnuOqZgTgnSQXn0PejDDY6TVZ8sJdZBgAmXn+4Qjzjc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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