We cut our Mongo DB costs by 90% by moving to Hetzner • Hacker News Board

Re: We cut our Mongo DB costs by 90% by moving to Hetzner

#121

Post by celsoazevedo » Thu, Nov 13, 2025, 8:32 PM UTC

dspillett wrote: post #81

0xbadcafebee wrote: post #17

> Here's how we managed to cut our costs by 90% You could cut your MongoDB costs by 100% by not using it ;) > without sacrificing performance or reliability. You're using a single server in a single datacenter. MongoDB Atlas is deployed to VMs on 2-3 AZs. You don't have close to the same reliability. (I'm also curious why their M40 instance costs $1000, when the Pricing Calculator ( https://www.mongodb.com/pricing )…

> You're using a single server in a single datacenter. This is a common problem with “bare metal saved us $000/mo” articles. Bare metal is cheaper than cloud by any measure, but the comparisons given tend to be misleadingly exaggerated as they don't compare like-for-like in terms of redundancy and support, and after considering those factors it can be a much closer result (sometimes down as far as familiarity and per…

It doesn't have to be one server in a single datacenter, though. It adds some complexity, but you could have a backup server ready to go at a different cheap provider (Hetzner and OVH, for example) and still save a lot.

Re: We cut our Mongo DB costs by 90% by moving to Hetzner

#122

Post by gizzlon » Thu, Nov 13, 2025, 8:34 PM UTC

kosherhurricane wrote: post #22

arbol wrote: post #8

Earlier quoted context omitted.

Atlas wasn't giving us any support for $3K per month. Hetzner at least have some channel to contact them, which is an improvement. That said, if their uptime is rubbish them we'll probably migrate again. Moving back to Atlas is not an option as we were getting hammered by the data transfer costs and this was only going to increase due to our architecture. Thanks for reading!

500GB isn't a lot of data, and $3K/month seems like an extortion for that little data. Having said that, MongoDB pricing page promises 99.995% uptime, which is outstanding, and would probably be hard to beat that doing it oneself, even after adding redundancy. But maybe you don't need that much uptime for your particular use case.

> Having said that, MongoDB pricing page promises 99.995% uptime

Or.. what? That's the important part

Re: We cut our Mongo DB costs by 90% by moving to Hetzner

#123

Post by rglover » Thu, Nov 13, 2025, 8:39 PM UTC

I love MongoDB's query language (JS/Node.js developer so the syntax fits my mental model well), but running a production replica set without spending tons of cash is a nightmare. Doubly so if you have any unoptimized queries (it's easy to trick yourself into thinking throwing more hardware at the problem will help). Lord help you if you use a hosted/managed service.

Just fixed a bug on my MongoDB instance last night that, due to a config error w/ self-signed certs (the hostname in the replica set config has to match the CN on the cert), that caused MongoDB to rocket to 400% CPU utilization (3x, 8GB, 4VCPU dedicated boxes on DO) due to a weird election loop in the replica set process. Fixing that and adding a few missing indexes brought it down to ~12% on average. Simple mistakes, sure, but the real-world cost of those mistakes is brutal.

Re: We cut our Mongo DB costs by 90% by moving to Hetzner

#124

Post by port11 » Thu, Nov 13, 2025, 8:40 PM UTC

0xbadcafebee wrote: post #17

> Here's how we managed to cut our costs by 90% You could cut your MongoDB costs by 100% by not using it ;) > without sacrificing performance or reliability. You're using a single server in a single datacenter. MongoDB Atlas is deployed to VMs on 2-3 AZs. You don't have close to the same reliability. (I'm also curious why their M40 instance costs $1000, when the Pricing Calculator ( https://www.mongodb.com/pricing )…

These types of posts make for excellent karma farming, but this one does present all the issues you've mentioned. Heck, Scaleway has managed Mongo for a bit more money and with redundancy and multi-AZ to boot. Were they trying to go as cheap as possible?

Re: We cut our Mongo DB costs by 90% by moving to Hetzner

#125

Post by celsoazevedo » Thu, Nov 13, 2025, 8:42 PM UTC

0xbadcafebee wrote: post #17

> Here's how we managed to cut our costs by 90% You could cut your MongoDB costs by 100% by not using it ;) > without sacrificing performance or reliability. You're using a single server in a single datacenter. MongoDB Atlas is deployed to VMs on 2-3 AZs. You don't have close to the same reliability. (I'm also curious why their M40 instance costs $1000, when the Pricing Calculator ( https://www.mongodb.com/pricing )…

> You have one server in one datacenter.

It doesn't have to be only one server in one datacenter though.

It's more work, but you can have replicas ready to go at other Hetzner DCs (they offer bare metal at 3 locations in 2 different countries) or at other cheaper providers like OVH. Two or three $160 servers is still cheaper than what they're paying right now.

Re: We cut our Mongo DB costs by 90% by moving to Hetzner

#126

Post by Too » Thu, Nov 13, 2025, 8:47 PM UTC

The dump, restore and custom scripts to synchronize the new instance sound a bit odd. You could just add the instance as a secondary to your cluster and mongo itself handles synchronization. Then removing the old instances automatically promotes the new to primary.

Re: We cut our Mongo DB costs by 90% by moving to Hetzner

#127

Post by gervwyk » Thu, Nov 13, 2025, 8:51 PM UTC

lxe wrote: post #110

0xbadcafebee wrote: post #17

> Here's how we managed to cut our costs by 90% You could cut your MongoDB costs by 100% by not using it ;) > without sacrificing performance or reliability. You're using a single server in a single datacenter. MongoDB Atlas is deployed to VMs on 2-3 AZs. You don't have close to the same reliability. (I'm also curious why their M40 instance costs $1000, when the Pricing Calculator ( https://www.mongodb.com/pricing )…

I think you underestimate how reduction in complexity can increase reliability. becoming a sysadmin for a single inexpensive server instance carries almost the same operational burden as operating an unavoidably very complicated cluster using a cloud provider.

not if you are using Atlas. Its as simple as it can be with way more functionality you can ever admin in yourself.

As others have said unless the scale of the data is the issue, if your switching because of cost, perhaps you should be going back to your business model instead.

Re: We cut our Mongo DB costs by 90% by moving to Hetzner

#128

Post by diffuse_l » Thu, Nov 13, 2025, 9:02 PM UTC

koakuma-chan wrote: post #94

0xbadcafebee wrote: post #17

> Here's how we managed to cut our costs by 90% You could cut your MongoDB costs by 100% by not using it ;) > without sacrificing performance or reliability. You're using a single server in a single datacenter. MongoDB Atlas is deployed to VMs on 2-3 AZs. You don't have close to the same reliability. (I'm also curious why their M40 instance costs $1000, when the Pricing Calculator ( https://www.mongodb.com/pricing )…

> You could cut your MongoDB costs by 100% by not using it ;) I cut my Mongo DB costs by 100% by piping my data to /dev/null.

At least it's ACID compliant

Re: We cut our Mongo DB costs by 90% by moving to Hetzner

#129

Post by speedgoose » Thu, Nov 13, 2025, 9:05 PM UTC

I wonder how many companies are running databases on non-encrypted storage on Hetzner.

Their bare-metal servers don't have storage encryption by default, and I don't know for sure about the VM hosts, as I don't have access, but Hetzner never claims that it is encrypted at rest. And there is no mention of storage encryption in their data protection agreement. https://www.hetzner.com/AV/DPA_en.pdf

Also, their data privacy FAQ mentions "you as the customer are responsible for both the data that is stored on your rented server and for the encryption of that data." https://docs.hetzner.com/general/general-terms-and-condition...

I would recommend, just in case, to set up LUKS on your server. You will find many guides for Hetzner.

If you don't do that, seeing your data in the wild is a real scenario. A few years ago, a Youtuber bought some used hard-drives in the hope to recover data to illustrate the risks of not erasing a hard-drive correctly. He eventually bought a hard-drive containing non-encrypted VM disks from Scaleway, a Hetzner competitor. My guess is that some hard drives disappeared before destruction after being decommissioned. Some customers got their shitty source code exposed on a 1.4M views video. Here is the first one: https://www.youtube.com/watch?v=vt8PyQ2PGxI

So, use LUKS.

Re: We cut our Mongo DB costs by 90% by moving to Hetzner

#130

Post by gervwyk » Thu, Nov 13, 2025, 9:10 PM UTC

arbol wrote: post #36

kosherhurricane wrote: post #22

Earlier quoted context omitted.

500GB isn't a lot of data, and $3K/month seems like an extortion for that little data. Having said that, MongoDB pricing page promises 99.995% uptime, which is outstanding, and would probably be hard to beat that doing it oneself, even after adding redundancy. But maybe you don't need that much uptime for your particular use case.

Its more like 700GB now on the new server and we were about to have to migrate to a higher tier on Atlas. > maybe you don't need that much uptime for your particular use case. Correct. Thanks for reading!

Did you have a very aggressive backup schedule?