Billing: how we charge for usage

Our model is flat per TB per month: you pay for the volume stored and nothing else. We don't charge for requests (PUT, GET, DELETE, LIST) or for egress (sending your data out). To keep that volume fair —and not dependent on a single point-in-time snapshot— we measure it once a day per bucket and prorate the cost day by day.

The model in one sentence

Each day we take the size of every one of your buckets, compute that day's accrued cost and, at the end of the month, sum the daily costs to issue your invoice. The result equals your average size for the month × the per-TB rate. If you only stored data for half the month, you pay roughly half.

Step 1: daily measurement per bucket

Once a day, OtterStorage takes a sample of each bucket: the space used (in bytes) and the number of objects. That measurement is the basis for billing and also feeds the usage charts you see in the console, both at the account level and in each bucket's detail.

Important: we work in binary base. A TB on your invoice is 1 TiB = 1024 GiB = 2⁴⁰ bytes (the same as S3 providers and most operating systems report).

Step 2: each day's accrued cost

With the day's sample we compute how much accrues that day. The formula is simple:

cost_for_the_day = (monthly_rate_per_TB × TB_measured_that_day) ÷ days_in_month

That is, each day contributes 1/N of a full month (where N is the actual number of days in that month: 28, 30, 31…), computed on the size you had that day. So if your bucket grows mid-month, you only pay the full rate for the days it actually used that space.

The rate depends on the bucket's disk technology (HDD, SSD or NVMe): each class has its own price per TB-month. See current amounts on the pricing page.

Step 3: monthly invoice

At month-end we automatically issue one invoice per account. The amount (the taxable base) is the sum of the daily accrued costs over the month. The invoice includes:

• Average TB-month for the account (the mean of the daily samples).
• Breakdown by disk class (HDD / SSD / NVMe), each with its rate and amount.
• Informational per-bucket annex: how much each bucket contributed to the total (not a separate tax line, but full transparency on where the cost comes from).
• VAT according to your tax profile.

If you have a wallet balance, it's applied first against the total; the rest is charged to your default payment method. You can see the full detail, download the PDF and review the breakdown from Billing in the console.

What is NOT billed

• API requests (PUT, GET, DELETE, LIST): we don't charge for them. We measure them only for information and to protect the service from abusive usage; you'll see them in the bucket detail with the note "informational · not billed".
• Egress / outbound transfer: downloading your data adds no cost.
• Ingress / inbound data: uploading or migrating data into OtterStorage is free (note that your source provider may charge its own egress when migrating).

Example

Suppose an example rate of €10/TB-month in a 30-day month:

• Days 1–15: the bucket holds 2 TB → each day accrues 10 × 2 ÷ 30 = €0.667 → 15 days = €10.00.
• Days 16–30: you upload more data and it holds 4 TB → each day accrues 10 × 4 ÷ 30 = €1.333 → 15 days = €20.00.
• Monthly invoice = €30.00 + VAT, equivalent to an average size of 3 TB over the month.

As you can see, it doesn't matter when in the month you upload or delete data: you pay for what you actually stored each day.

Frequently asked questions

Do I pay if I upload and delete data on the same day? +

Billing is based on the daily sample of the bucket size. If the data isn't present at the moment of the daily measurement, it doesn't count that day. That's why the cost reflects your real usage across the month, not a one-off spike.

Do you charge per request or per download? +

No. We don't charge for requests (PUT/GET/DELETE/LIST) or for egress. We only bill storage per TB-month. Operations are measured purely for information and to protect the shared cluster.

Is a TB 1000 or 1024 GB? +

We use binary base: 1 TB = 1 TiB = 1024 GiB = 2⁴⁰ bytes. It's the same criterion S3 services and most operating systems use when reporting size.

When is the invoice issued and how is it charged? +

It's issued automatically at the end of each month. Wallet balance is applied first and the rest is charged to your default payment method (card, SEPA direct debit or PayPal). You'll find the PDF and breakdown in the Billing section of the console.

Can I see where my cost comes from? +

Yes. The invoice includes a breakdown by disk class and an informational per-bucket annex, and the console shows daily usage charts per account and per bucket.