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Ask HN: How can I estimate hosting costs for an app?

12 points by JakeWesorick ↗ HN
I have a Ruby on Rails app hosted on Heroku. The project is fairly far along, to the point where we are in talks with investors. We have all our numbers down except when it comes to hosting costs. How can I estimate what my hosting costs will be as my user base grows?

10 comments

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JakeWesorick
Possible side question: What does hosting your app cost right now?
deedubaya
I'm going on a road trip. I'll be driving on the interstate, and have already gone half way.

How much gas will I use?

JakeWesorick
The same amount that it took to get you where you are right now? I also am sensing you are trying to make a joke. While I may be very ignorant in this area I'm not looking to made fun of, just for someone to educate me on what is wrong with the question.
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dschwartz88
This is an awful oversimplification, but in my experience, there are two different kinds of applications:

- User-centeric (think: an e-commerce site): your costs are going to grow somewhat linearly with your userbase/traffic. Do a load test to figure out how many concurrent users each dyno supports and then model your costs with that in mind.

- Data-centric (think: an analytics platform): your costs are to going to grow linearly with the amount of data points each customer is going to be using. Figure out how many data points a single worker dyno (running 24x7) can process and then model your costs with that in mind.

fataliss
You can also have a combination of both. But basically I second this post, you have to figure out what is going to increase as your product gain momentum. If you will be handling millions of requests because each client is going to do plenty of them, are they going to store data... Like if you were Netflix, you would have to consider the number of users growing, but also the size of your catalogue. Try to define what direction your business is going as it grows and then you will be able to narrow down the costs more accurately.
rizz0
It also depends on how much you'll able to cache.
webnrrd2k
Just a thought: Would it be worth it to run a test site and simulate some traffic? I think that would give you the best numbers for your app.
shawnreilly
You need to determine the cost per User. Different Users might represent different Usage Patterns, so I'd be looking for averages. If the Product is already in production and you have an existing user-base, this is how I'd do it; Correlate your user-base statistics (number of Users) in relation to your hosting costs at different milestones and/or points in time. This metric will give you some insight into how much it costs per User at different stages of growth. This could include the growth of the user-base as well as the growth of your Product (in terms of features and/or infrastructure changes). You would want to identify any trends and/or variations with the resulting averages over time. This will give you some data to work with in terms of making projections.