SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f4f917886eee0a41868d19e64196d3d39603815765f6705b67473c722666ae90' 
  AND token = '6VnNhsNQvHAm7xS2RJcHtZNGaQanqL5JLwDwkc+b5bI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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