SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '826b0613de50864c686a20ba60d960c8836ffed5b89fe4256d0e91b006943c0d' 
  AND token = 'KssL2tchP9m1RqxV+DYHQIL/wlM5kzmlccGWPYQBIq4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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