SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cac41e068386b4036f0bccc6dbd0be107f6f92d072f4a411fa31d47db1aa3f65' 
  AND token = 'MW0aam5Kgm0UPYjRyaKr7VbmQ+WJdkn8ZAJGnM/Cla0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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