SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a0cf3761807789e24e176cbb4f556a4a8721ee975bdf4f3e347eb174cb7f386f' 
  AND token = 'COl5NgrhtRFuLhLm/GY4fupbsH+LJO8njpM2+HJDnCQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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