Companies that rent computing on demand, servers, storage, databases, by the hour, so you don't buy or run hardware.
Why it exists
Buying, housing, and maintaining your own servers is slow, costly, and hard to scale up or down with demand. Cloud providers exist to rent computing, storage, and services on demand, so you pay for what you use and can grow or shrink in minutes.
How it actually works
Instead of buying machines, you rent whatever you need from Amazon (AWS), Google (GCP), or Microsoft (Azure), and give it back when done. Need ten servers for a sale? Spin them up for the day, then release them. You pay for usage.
The cloud provides not just raw servers but managed databases, queues, storage, and more, so small teams can run infrastructure that once needed a dedicated department.
A senior PM walks you through it
A junior PM, stuck
Finance forwarded me the AWS bill and it is roughly double last month, right after the Eid campaign. They want me to explain what TiffinBox is actually paying for and whether something is wrong. I have never opened a cloud bill in my life and I do not want to answer "I will ask engineering" to a finance question I should be able to read myself.
A cloud bill is an itemized list of rented resources, and you pay per resource by how much you use it, so "doubled" almost always traces to one line that moved, not a mystery. Reading one down to the line that matters takes about five minutes and no engineering. This is the bill, trimmed to the four lines that carry the story. Read it top to bottom, then take the steps with me.
AWS invoice, TiffinBox, Eid campaign month
Line items
EC2 (the app servers, billed by instance-hours) tripled during Eid week, back to baseline after
RDS (the managed Postgres database) flat, same as every month
S3 (menu and banner image storage) up slightly, more images added
Data transfer out (bytes served to customers) up, in step with the traffic spike
Summary
Total: about 2x last month, almost all of the increase on the EC2 line.
Billing model: pay per usage, per hour, no fixed contract.
Click a step to see the lines it points at.
Mistakes I've seen
Answering Finance with the total instead of the line item. "The bill doubled" invites a panic; "EC2 tripled for Eid week then dropped back" is a precise, calm answer they can file.
Assuming a spike is waste. Usage that maps to a campaign is the pay-per-use model doing its job; the thing to actually watch for is a line that rises and never comes back down.
Not knowing which lines are fixed versus usage-driven. RDS costs the same busy or idle while EC2 and data transfer scale with load, and mixing the two up leads to chasing the wrong line for savings.
Treating the cloud bill as an engineering-only document. Cost per feature is a genuine product input, and a PM who can read the bill can weigh "this feature is expensive to run" instead of learning it after launch.
Reply to Finance: "The increase is almost entirely the EC2 line, the app servers. We autoscaled extra servers for the Eid campaign and released them after, so it tracks the campaign and is already back to baseline. Nothing is wrong." You just read a cloud bill by its line items and tied the movement to an event, which works on every bill you will be forwarded.
Where a PM meets this
Cloud cost is a real line item that scales with usage; "this feature is expensive to run" is a genuine consideration.
Which provider and region affects speed, cost, and sometimes legal data-residency requirements, all product-adjacent.
Hear it in a meeting
"We'll autoscale on AWS for the campaign, then scale back down."