SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6f10743b8e3fbd6fdcab698c6d6f002d1bc07a743b191f1808f93865812ec6a' 
  AND token = '3W9BJq5d1T+pSAQJpeSw8zE/BCcIBGUoj3YAF1PMHjw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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