Are there any best practices about what data structures to use (or are more efficient) with DO)? thx

I mean, the only thing I really have to say is balance. You want to keep as much in memory as possible to be able to query it, but DOs can only store values that are so large

One question regarding pricing. It says in the pricing page:

2. Duration billing charges for the 128 MB of memory your Durable Object is allocated, regardless of actual usage. If your account creates many instances of a single Durable Object class, Durable Objects may run in the same isolate on the same physical machine and share the 128 MB of memory. These Durable Objects are still billed as if they are allocated a full 128 MB of memory.

I'm using DO to store user data. If user's are creating instances (small) of the same class , does it mean they will run in the same 128MB (as much as it can fit in) and billed once?

Another question: I understand when a DO finishes all I/O operation, Promsies .... is not active anymore, and then evicted from memory (and not billed)?

Durable Object lifespan
A Durable Object remains active until all asynchronous I/O, including Promises, within the Durable Object has resolved.

But then here it says:

In-memory state in a Durable Object
Variables in a Durable Object will maintain state as long as your Durable Object is not evicted from memory. A common pattern is to initialize an object from persistent storage and set instance variables the first time it is accessed. Since future accesses are routed to the same object, it is then possible to return any initialized values without making further calls to persistent storage.

What does

to return any initialized values

mean? how are values kept in memory once the DO is not active anymore?

Memory and storage aren't the same. You can store up to your account limit (50GB) across many or a single DO. It means any values you retrieve at DO init from storage and set in memory. Values aren't kept in memory when evicted anything you don't save to storage will be gone.

Regarding the 50 GB account limit, how much can you really raise it? Or if I keep needing more would I inevitably have to move to R2 or something else?

In this case memory means any variables that are on the DO class, instead of stored in the DO key-value store (which is persistent storage).

Like, it can be raised?

But not many TB.

So depends on the size of your data.

I wouldn't even count on a single TB tbh

I see.

I don't really see any reason they would not give you that much storage 🤔 I mean maybe you'll need an ENT contract at that point but

Yeah definitely can’t afford that 😅

you could always submit the google form limit increase and see what they say 🤷

I need a strong consistency “read-modify-write” storage for user generated content, using DO storage is the obvious choice but the 50 GB limit is a thing

The second option would be DO doing the modification and writing logic to R2, but DO charges for wall clock time so that’s a bit unfortunate.

This sounds like something just R2 might be useful for?

it's strongly consistent by design

What if a second request comes in when the previous r-m-w is not yet finished?

Yeah R2 doesnt have that level of consistency. I would just submit a limit increase and see what happens. Maybe even at 1TB or more you wouldnt need an ENT contract but who knows unless you submit a request 🤷

But also 50GB still is a lot are you sure you even need more than that?

Nope don’t know how much I actually need, just thinking ahead, I’ll send in a form and see what they say.

In the docs it says something about multiple DOs of the same class can run in the same isolate and share memory, does that mean it’s not a guarantee that each DO will always have 128 MB of memory at its disposal?

yes but very unlikely because that means 2 DOs have to be created on the exact same server and be active at the same time

I see.

It just hit me that I need the entire object to be in memory to do the r-m-w and that might be a bit of an issue with DO.

if your object doesnt fit in memory it wont fit in a DO value either so there might be some more problems given that 😛

its like 128KB for a value?

Well I could always split it and store into multiple keys.