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Part 6 of 7 · Domain renewal watcher series ~5 min read

What the domain renewal watcher costs

This is the cheapest system in the whole series. Eleven domains checked weekly is fewer than fifty lookups a month, each one an HTTPS request that costs nothing, and there is no model anywhere in it. Here is where each cent goes.

Key takeaways

  • About $1 a month at 150 lookups. Roughly $2 at 600 lookups.
  • One Bedrock read per lookup is the only line that scales. Everything else is rounding.
  • Nothing is always-on, so a quiet month genuinely costs almost nothing.
  • RDAP lookups are free HTTPS requests and there is no model at all, so this is essentially a fixed-cost system.
  • The duplicate test runs before the read, so resends are free.
  • The three real risks: a retry loop, storage nobody expires, and a bigger model than the job needs.

The bill at three volumes

These are US East prices at the time of writing, at three volumes that bracket most small businesses. Find the bar closest to your own and read across.

Monthly cost of the domain renewal watcher at three volumesA stacked bar chart with three bars, one per volume tier: 50 lookups totalling about $1, 150 lookups totalling about $1, and 600 lookups totalling about $2. Each bar is stacked from bands. The largest and fastest-growing is Bedrock, one read per lookup, in teal. Then SES for the messages, in pink. Then S3 and DynamoDB storage in green. Then a fixed orange band for Secrets Manager and AWS Budgets, which is eighty-six cents at every volume. Then a grey band for Lambda, SQS and CloudWatch. A note says the read is the only bar that grows with the business and the orange band never moves.$0$1$2$3$4~$1.3250 lookups~$1.47150 lookups~$2.16600 lookupsBedrock — one read per lookupSES — asks, results, receiptsS3 + DynamoDBFixed — Secrets Manager, BudgetsLambda, SQS, CloudWatchThe read is the only bar that grows with the business. The orange fixed band never moves.
Fig 1. The monthly bill at three volumes. The teal band — one model read per lookup — is the only part that grows; the orange fixed band is the same 86 cents at every volume.

Line by line

LineAt 150 lookupsHow it scales
Bedrock read$0.00Linear. One call per lookup, roughly 1,800 in and 200 out tokens.
SES$0.08Linear. About 0.15 messages per lookup.
DynamoDB + S3$0.30Storage grows with what you retain, not with throughput.
Lambda + SQS$0.12Linear, and effectively free at this scale.
CloudWatch$0.16Flat, if you set retention. Unbounded if you do not.
Secrets Manager$0.40Flat. One secret, $0.40 a month.
AWS Budgets$0.46Flat. Two actions, so you find out before the bill does.

There is no read line at all here: nothing in this system calls a model. The bill is the fixed band plus a handful of emails, which is why it comes in around a dollar.

The three ways this bill surprises you

Every one of these has happened to somebody, and all three are cheap to prevent.

  • Fetching the bootstrap on every lookup. The IANA bootstrap file is a few hundred kilobytes and changes rarely. Fetching it per domain per week is wasteful and impolite; cache it weekly.
  • Certificate log searches on every run. Discovery is a monthly job, not a weekly one. Domains do not appear that fast and the searches are the only meaningful outbound cost.
  • Log retention left at never. With a bill this small the logs will be a hundred per cent of it within months.

What it costs when nothing happens

This matters more than the headline number for a seasonal business. In a month with nothing to process the bill is the fixed band: Secrets Manager at forty cents, AWS Budgets at forty-six, and a few cents of storage. Call it a dollar. There is no instance to stop and nothing to remember to turn off.

The monthly bill at four volumes plus one failure modeA horizontal row of five boxes. Quiet month, about one dollar. 50 lookups, about $1. 150 lookups, about $1. 600 lookups, about $2. And one bad retry loop, about two hundred dollars. A note says four of these are the design working and the fifth is a missing dead-letter queue.THE BILL, AT A GLANCEQuiet month~$150 lookups~$1150 lookups~$1600 lookups~$2One bad loop~$200Four of these are the design working. The fifth is a missing dead-letter queue.
Fig 2. The bill at a glance, including the one that is not a volume at all. A retry loop with no dead-letter queue costs more than every legitimate use of the system put together.
  • Management
  • Analytics
  • Front-end & mobile

Set these on day one

  • A dead-letter queue on every SQS queue, with a maximum receive count of three.
  • Thirty-day retention on every CloudWatch log group. There is no default that is safe.
  • An S3 lifecycle rule on the object prefix, tiering at 90 days and expiring at your actual record-keeping horizon.
  • Two AWS Budgets actions — one that emails at half your expected spend, one at double it. The second is how you find out about a loop in an hour instead of a month.
  • Provisioned concurrency: none. Nothing here is latency-sensitive enough to justify paying for a warm function.

Next: the same system drawn for engineers — service names, resource identifiers, IAM scopes, table schemas and the model id.

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