sqllite read/write queue concern with django - django

Question

I'm building a website where college students can order delivery food. One special attribute about our site is that customers have to choose a preset delivery time. For example we have a drop at 7pm, 10pm, and at midnight.
All the information about the food is static (ie price, description, name), except the quantity remaining for that specific drop time.
Obviously i didn't want to hardcode the HTML for all the food items on my menu page, so i wrote a forloop in the html template. So i need to store the quantity remaining for the specific time somewhere in my model. the only problem is that I'm scared that if i use the same variable to transport the quantity remaining number to my template, i'll give out wrong information if alot of people are accessing the menu page at the same time.
For example, lets say the 7pm drop has 10 burritos remaining. And the 10pm drop has 40 burritos. Is there a chance that if someone has faster internet than the other customer, the wrong quantity remaining will display?
how would you guys go around to solve this problem?
i basically need a way to tell my template the quantity remaining for that specific time. and using the solution i have now, doesn't make me feel at ease. Esp if many people are going to be accessing the site at the same time.
view.py
orders = OrderItem.objects.filter(date__range=[now - timedelta(hours=20), now]).filter(time=hour)
steak_and_egg = 0
queso = 0
for food in orders:
if food.product.name == "Steak and Egg Burrito":
steak_and_egg = steak_and_egg + food.quantity
elif food.product.name == "Queso Burrito":
queso = queso + food.quantity
#if burritos are sold out, then tell template not to display "buy" link
quantity_steak_and_egg = max_cotixan_steak_and_egg - steak_and_egg
quantity_queso = max_cotixan_queso - queso
#psuedocode
steakandegg.quantity_remaining = quantity_steak_and_egg
queso.quantity_remaining = quantity_queso
HTML:
{% for item in food %}
<div id="food_set">
<img src="{{item.photo_menu.url}}" alt="" id="thumbnail photo" />
<div style='overflow:hidden'>
<p id="food_name">{{item.name}}</p>
<p id="price">${{item.price}}</p>
</div>
<p id="food_restaurant">By {{item.restaurant}}</p>
<div id="food_footer">
<img src="{{MEDIA_URL}}/images/order_dots.png" alt="" id="order_dots" />
<a id ="order_button" href="{{item.slug}}"></a>
<p id="quantity_remaining">{{item.quantity_remaining}} left</p>
</div><!-- end food_footer-->
</div><!-- end food_set-->

Answer 1

I don't understand what "faster Internet" or "using the same variable" have to do with anything here (or, indeed, what it has to do with sqlite particularly).
This question is about a fundamental property of web apps: that they are request/response based. That is, the client makes a request, and the server replies with a response, which represents the status of the data at that time. There's simply no getting around that: you can make it more dynamic, by using Ajax to update the page after the initial load, which is what StackOverflow does to show update messages while you're on the page. But even then, there's still a delay.
(I should note that there are ways of doing real-time updates, but they're complicated, and almost certainly overkill for a college food-ordering website.)
Now the issue is, why does this matter? It shouldn't. The user sees a page saying there is 1 burrito left - perhaps with a red warning saying "order quickly! almost gone!" - and they press the order button. On submission of that order, your code presumably checks for the actual status at that time. And, guess what, in the meantime you've processed another order and the burrito has already gone. So what? You simply show a message to the user, "sorry, it's gone, try something else". Anyone with any experience ordering things on the web - say, concert tickets - will understand what's happened.