SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81e87f73c415d54f9c857301d0b8a205c14fa5f8a85937350e33d28c41ade268' 
  AND token = 'X9glZn9wH3gOtvIiPbdLU6pS5gGky1pcPC+DzFIGABU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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