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Part 6 of 7 · Address verifier series ~5 min read

What the address verifier costs

The AWS side of this is almost free and the reference lookups are not, which makes the cache the most important cost decision in the design. Eight thousand lookups a month is a busy small e-commerce business including its background sweep. Here is where each cent goes.

Key takeaways

  • About $45 a month at 8,000 lookups. Roughly $167 at 30,000 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.
  • The reference lookups are the whole bill, and a 70% cache hit rate cuts them by 70%.
  • 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 address verifier at three volumesA stacked bar chart with three bars, one per volume tier: 2,000 lookups totalling about $12, 8,000 lookups totalling about $45, and 30,000 lookups totalling about $167. 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$50$100$150$200~$12.262,000 lookups~$45.348,000 lookups~$166.630,000 lookupsBedrock — one read per lookupSES — asks, results, receiptsReference lookups — cache misses onlyS3 + 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 8,000 lookupsHow it scales
Bedrock read$0.00Linear. One call per lookup, roughly 1,800 in and 200 out tokens.
Reference lookups$32.00Linear at $0.0040 per lookup.
SES$4.02Linear. About 0.02 messages per lookup.
DynamoDB + S3$1.56Storage 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.

Reference lookups are charged per query by whichever provider you use and only bill on a cache miss. The AWS compute is a few cents; the provider is the bill.

The three ways this bill surprises you

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

  • Caching on the raw string. The single most expensive mistake available here: three spellings of one address become three paid lookups, and the hit rate collapses from seventy per cent to near zero.
  • Sweeping the whole database repeatedly. A full re-sweep every quarter is eleven thousand lookups for almost no new finding. Re-check on use, not on a schedule.
  • Log retention left at never. Address lookups log per request and the volume is high enough that unbounded retention becomes the second-largest line.

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. 2,000 lookups, about $12. 8,000 lookups, about $45. 30,000 lookups, about $167. 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~$12,000 lookups~$128,000 lookups~$4530,000 lookups~$167One 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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