These questions always sound flawed to me. It's like asking won't I regret moving to California and paying high taxes once I start making millions of dollars? Maybe? But that's an amazing problem to have and one that I may be much better equipped to solve.
If you are small, RDS is much cheaper, and many company killing events, such as not testing your backups are solved. If you are big and you can afford a 60K/yr RDS bill than you can make changes to move on-prem. Or you can open up excel and do the math if your margins are meaningfully affected by moving on-prem.
On some level, AWS/GCP/California relies on you doing this calculation for the things that you can do it on easily (the savings of moving away), while not doing this calculation on things where it's hard to do (new development). That way, you can pretend that your new features are a lot more valuable than the $Xk/year you will save by moving your infra.
Yes, I've done the math. The piece you are missing is, saving money on infra will bring in $0 new dollars. There is a floor to how much money I can save. There is no ceiling to how much money the right feature can bring in. Penny pinching on infra, especially when the amount of money is saved is less than the cost of an engineer is almost always a waste of time while you are growing a company. If you are at the point where you are wasting 1x,2x,3x of an engineers salary of superflous infrastructure - then congratulations you have survived the great filter for 99% of startups.
>That way, you can pretend that your new features are a lot more valuable than the $Xk/year you will save by moving your infra.
Finding product market fit is 1000x harder than moving from RDS to On-prem. If you haven't solved PMF, then no amount of $Xk/year in savings will save you from having to shut down your company.
The thing is, most features, particularly later in the life of a company, don't have an easy-to-measure revenue impact, and I suspect that many features are actually worth $0 of revenue. However, they cost money to implement (both in engineering time and infra), making them very much net negative value propositions. This is why Facebook and Google can cut tons of staff and lose nothing off their revenue number.
Also, there's a bit of a gambling mentality here which is that a feature could be worth effectively infinite revenue (ie it could be the thing that gives you PMF), so it's always worth doing over things with known, bounded impact on your bottom line. However, improving your efficiency gives you more cracks at finding good features before you run out of money.
No one runs their own electricity supply (well until recently with renewables/storage), they buy it as a service, up to a pretty high scale before it becomes more economic to invest the capex and opex to run your own.
I mean, I'm looking after a 4 instance Aurora cluster which is great feature wise, is slightly overprovisioned for special events, and is more likely to shrink than grow 2x in the next decade. If we start experiencing any issues, there's lots of optimisations that can be still gained from better caching and that work will be cheaper than the instance size upgrade.
There’s still a defined cost to swapping your DB code over to a different backend. At the point where it becomes uneconomical, you’re also at a scale you can afford rewriting a module.
That’s why we have things like “hexagonal architecture”, which focus on isolating the storage protocol from the code. There’s an art to designing such that your prototype can scale with only minor rework — but that’s why we have senior engineers.
So moving to/from Aurora/RDS/own EC2/on-prem should be a matter of networking and changing connection strings in the clients.
Your operational requirements and processes (backup/restore, failover, DR etc) will change, but that's because you're making a deliberate decision weighing up those costs vs benefits.
You can use DNS to mitigate the pain of changing those connection strings, decoupling client change management from backend change process, or if you had foresight, not having to change client connection strings at all.
I mean, DNS change can work, but when you're doing that one-in-years change, why risk the extra failure modes.