Lost property matcher
A small system for anywhere the public leaves things behind: a photograph and three fields at the moment of finding, structural matching of claims that arrive days later and describe the item badly, an ownership test that does not hand the answer to the claimant, and a retention policy that ends in a recorded outcome rather than a bin bag. Seven posts on the same system, one diagram at a time, with a cost breakdown and an engineering reference at the end.
- 01
A lost property matcher on AWS for a few dollars a month
The whole system on one page — logging, matching, return, disposal — and why the ninety seconds at the start determines whether any of the rest works.
- 02
How a found item gets logged in ninety seconds
Why the logging step has a hard time budget, the three fields that matter, controlled categories instead of free text, and what to do about high-value finds.
- 03
How a claim gets matched to an item
Which parts of a claim are reliable, structural matching on zone and time, why the model normalises rather than decides, and what the shortlist is for.
- 04
How an item gets back to its owner
Testing ownership without leaking the answer, collection and postage, chain of custody for valuables, and what the closing record has to contain.
- 05
What happens to what is never claimed
Setting retention periods by category, the disposal routes and their pitfalls, why staff taking items needs an explicit rule, and what the disposal record proves.
- 06
What the lost property matcher costs
About $2 a month. One Bedrock read per claim is the only line that grows; the queue, the table, the mail and the storage are rounding errors. Plus the three ways the bill could surprise you.
- 07
Engineering reference: the lost property matcher architecture
Same system, drawn purely for engineers. Service names, region, Lambda inventory, IAM scopes, the schemas and the exact model id.
Frequently asked questions
- What is a lost property matcher?
- A small serverless system that records found items at the moment they are found, matches incoming claims against them on structure rather than description, and drives each item to a recorded outcome: returned, disposed of, or donated.
- Why not just let claimants look through photos?
- Because it removes the only ownership test you have. Once somebody has seen the item, they can describe it perfectly, and you have no way of telling an owner from an opportunist.
- How long should items be kept?
- By category, not uniformly: perishables the same day, ordinary items around a month, valuables and identity documents considerably longer with a recorded chain of custody. The specific periods are a policy decision; having them written down is the part that matters.
- What about a found phone or laptop?
- Log it, do not open it, and charge it only if that is how you will reach the owner through a lock screen message. The contents are somebody else’s data and the safest position is that nobody in your business has looked at them.
- What does it cost to run?
- A couple of dollars a month. See part six.