How do I mock the Amazon DynamoDB API locally?

Install stunt, add a one-service block to stunt.yaml (adapter: embedded:dynamodb-style), and run stunt up. You get a local, stateful stand-in for Amazon DynamoDB API 2012-08-10 — 1 routes over rest — with no remote account, no network, and no bills.

Is the Amazon DynamoDB API mock data synthetic?

Yes — entirely. The adapter returns generated data only; stunt's adapter lint rejects real-looking secrets and PII at build time. It simulates the shape and behavior of Amazon DynamoDB API (routes, status codes, pagination, webhooks), never real records.

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dynamodb-style

simulates Amazon DynamoDB API 2012-08-10

restadapter v0.1.01 routes

verification

SDK + VMverified with aws-sdk-go-v2 v1.47.1· surface 1 · not implemented 8 · differs 5

use it

# add to stunt.yaml
services:
  dynamodb:
    adapter: embedded:dynamodb-style

# then
$ stunt up

The embedded: source extracts this adapter from the binary — no git clone, fully offline.

how to mock the Amazon DynamoDB API locally

Install stunt, paste the service block above into stunt.yaml, run stunt up — then point your client at localhost instead of Amazon DynamoDB API. It works offline, keeps state across requests and restarts, and every response is synthetic: the route shapes, status codes, pagination, and webhook delivery follow the real Amazon DynamoDB API 2012-08-10 surface — the data is fake, the behavior is real.

backing stores

tablesitems

api surface (1)

generated from the adapter manifest — exactly what boots, nothing more

1 routes

POST/

SDK-verified behaviors (8)

✓CreateTable via real SigV4
✓typed item Put/Get round-trip (S/N/BOOL/SS)
✓UpdateItem SET/ADD with exact decimal arithmetic
✓ConditionExpression → ConditionalCheckFailedException
✓Query numeric sort-key ordering (1,2,10)
✓Query BETWEEN + ScanIndexForward=false
✓Scan with FilterExpression
✓typed ResourceNotFoundException surface

VM-verified behaviors (22)

✓an unsigned request is 403; a real SigV4 signature passes
✓tampered signatures, wrong secrets, and clock skew are all 403
✓CreateTable returns ACTIVE; duplicate and bad-schema creates throw the real exceptions
✓Describe/List/Delete round out the lifecycle with table paging
✓typed values round-trip verbatim through PutItem/GetItem
✓projection, misses, and malformed keys take the documented paths
✓SET upserts, ADD does exact-decimal math, REMOVE drops with UPDATED_OLD
✓non-numeric ADD and bogus ReturnValues are ValidationExceptions
✓numeric sort keys order numerically (10 after 9)
✓BETWEEN, >=, descending, and begins_with shape the key range
✓Limit + ExclusiveStartKey pages queries; bad conditions are rejected
✓Scan returns the whole table and filters by expression
✓Select COUNT, pagination, and error paths round out Scan
✓attribute_not_exists guards writes; failed checks return the old item
✓conditional deletes enforce the condition; consumed capacity echoes
✓batch writes and gets round-trip with empty Unprocessed maps
✓oversized, unknown-table, and invalid batches are rejected atomically
✓unsupported constructs fail with named ValidationExceptions
✓a leading "." answers ValidationException instead of wedging the tokenizer
✓"|" in key values cannot collide two composite keys
✓set members dedupe by string and numeric value
✓"-0" and "0" name the same stored item

Not implemented (8)

No secondary indexes: GSI/LSI creation and index-targeted queries
No transactions: TransactGetItems, TransactWriteItems
No PartiQL: ExecuteStatement, BatchExecuteStatement
No TTL: DescribeTimeToLive, UpdateTimeToLive
No backup or restore: CreateBackup, RestoreTableFromBackup
No UpdateTable, TagResource/UntagResource/ListTags, or DescribeLimits
No PITR or import/export: ExportTableToPointInTime, ImportTable
No global tables (CreateGlobalTable, ListGlobalTables)

Differs from the real API (5)

expression subset: OR/NOT/parens/IN/size()/doc paths rejected as ValidationException
tables are ACTIVE immediately and DeleteTable is synchronous; no CREATING/DELETING
UnprocessedKeys/UnprocessedItems always empty; no throttling, ConsumedCapacity fixed at 1
Query/Scan Limit caps returned post-filter items; real caps items evaluated
UpdateItem REMOVE on a key attribute silently no-ops instead of erroring

full scorecard →

want more of the Amazon DynamoDB API surface? adapters are YAML + Starlark — the authoring guide covers adding routes, fixtures, and state machines. Open an issue for anything big first, or just file a PR — merged routes ship in the next release.