SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a0733243e1eec6ed055716cd5a49b28e3744f2e79f91513224da94b5d4da6f21' 
  AND token = 'YZqJqPElT50T8QlAOjI9uajLbuQxjZ/fgtbOMowVh3s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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