SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '138a6312b1c763fc68bc71193f48230afd82362a49ba5326c596bc82165b4d4e' 
  AND token = '6xe3XkafMRXpSJCiq5Mb+PBekwd6+KqtGuqCzzgKlFc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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