DynamoDB Nodes

Amazon DynamoDB is AWS's serverless NoSQL key-value and document database. MaestroHub provides six nodes covering the single-item operations and the two multi-item reads, so a pipeline can look a record up, read a partition, write results back, or clean up — all against the table its connection profile names.

Items cross the boundary as plain JSON in both directions. You write {"deviceId": "line3"}, not DynamoDB's {"deviceId": {"S": "line3"}}, and a downstream node reads result.item.celsius rather than result.item.celsius.N.

Configuration Quick Reference

Field	What you choose	Details
Parameters	Connection, Function, Function Parameters, Timeout Override	Select the connection profile (which fixes the table), the function, values for any ((parameter)) the function uses, and optionally a timeout override.
Settings	Description, Timeout (seconds), Retry on Timeout, Retry on Fail, On Error	Node description, maximum execution time, retry behavior on timeout or failure, and error handling strategy. All execution settings default to pipeline-level values.

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DynamoDB Get Item Node

DynamoDB Get Item Node

Fetch one item by its full primary key — the partition key, plus the sort key when the table has one.

A key that matches nothing is not an error. The node succeeds with result.found false and no item, so a pipeline branches on the lookup instead of routing it through failure handling.

Supported Function Types:

Function Name	Purpose	Common Use Cases
Get Item	Read a single item by primary key, optionally projecting a subset of attributes	Enrichment lookups, device shadow reads, existence checks before a write

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DynamoDB Query Node

DynamoDB Query Node

Read the items in a single partition, narrowed by a sort-key condition and an optional filter.

This is the efficient multi-item read: DynamoDB only reads the keys the condition selects. Reach for it whenever the partition key is known.

Supported Function Types:

Function Name	Purpose	Common Use Cases
Query	Read one partition using a key condition, optionally against a secondary index and in descending sort order	Time-window reads per device, a customer's orders, newest-first feeds

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DynamoDB Scan Node

DynamoDB Scan Node

Read items across every partition, optionally narrowed by a filter expression.

A scan reads the whole table, so prefer Query when a partition key is known. Scan earns its place on exports, backfills and small reference tables.

Supported Function Types:

Function Name	Purpose	Common Use Cases
Scan	Read across the table with an optional filter, paging through result.lastEvaluatedKey	Table exports, migration sweeps, auditing rows against a condition

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DynamoDB Put Item Node

DynamoDB Put Item Node

Write one item, replacing any existing item with the same primary key.

Add a condition expression to make the write conditional — attribute_not_exists(pk) turns a replace into an insert-only. A condition that fails is reported as a permanent error, so the node fails at once instead of draining its retries, and its On Error setting decides what happens next.

One consequence to know if the node is buffered by store-and-forward: an insert-only write whose acknowledgement was lost fails its condition on replay and dead-letters, even though the first attempt stored the item.

Supported Function Types:

Function Name	Purpose	Common Use Cases
Put Item	Write a complete item, optionally guarded by a condition expression	Persisting pipeline output, upserting profiles, insert-only writes

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DynamoDB Update Item Node

DynamoDB Update Item Node

Change named attributes of the item at a primary key, leaving the rest untouched.

DynamoDB creates the item when it does not exist, unless a condition expression forbids it. ADD and SET arithmetic make this the node for counters and running totals.

SET and REMOVE converge when store-and-forward replays a buffered write. ADD and list_append accumulate instead, so a replayed increment counts twice. Where that matters, compute the value upstream and write SET counter = :value.

Supported Function Types:

Function Name	Purpose	Common Use Cases
Update Item	Apply SET, ADD, REMOVE or DELETE clauses to one item	Status flags, counter increments, appending to a list, merging new fields

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DynamoDB Delete Item Node

DynamoDB Delete Item Node

Delete the item at a primary key.

Deleting an item that does not exist succeeds and changes nothing, which makes this node safe to replay.

Supported Function Types:

Function Name	Purpose	Common Use Cases
Delete Item	Remove one item by primary key, optionally guarded by a condition expression	Retention cleanup, erasure requests, compensating actions after a failed step

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Paging through a Query or Scan

Limit is sent to DynamoDB, so it bounds what the service reads rather than trimming a full result set afterwards. Two consequences worth knowing before you build a loop:

• A filter expression is applied after the items are read and before Limit. A selective filter can therefore return far fewer items than Limit — even zero — while more items still remain.
• Because of that, an empty result.items is not the end of the data. result.lastEvaluatedKey is: it is present exactly while more items remain, and absent on the last page.

To read a whole table, feed result.lastEvaluatedKey back in as the next run's Exclusive Start Key and stop when it is absent (result.truncated says the same thing as a boolean).

Output

Every DynamoDB node delivers its data under result, and execution facts (success, functionId, durationMs, timestamp) under _metadata:

Node	Expression	Description
All nodes	$node["Name"].result.table	The table the operation ran against
Get Item	$node["Name"].result.found	Whether an item exists at that key — a miss is a normal result, so branch on this rather than on failure
	$node["Name"].result.item	The item as plain JSON, or null when found is false. $node["Name"].result.item.<attribute> reads a value
Query, Scan	$node["Name"].result.items	The matching items, one object each. $node["Name"].result.items[0].<attribute> reads a value
	$node["Name"].result.count	How many items were delivered, after any filter expression
	$node["Name"].result.scannedCount	How many items DynamoDB examined to produce them — larger than count means a filter discarded the difference, which is the signal that an index would do the work more cheaply
	$node["Name"].result.truncated	Whether more items remain — true exactly when lastEvaluatedKey is present
	$node["Name"].result.lastEvaluatedKey	The cursor to resume from, absent on the last page. Feed it back as the next run's Exclusive Start Key
Put Item, Update Item, Delete Item	$node["Name"].result.attributes	The item the function's Return Values setting asked for — absent when that setting is NONE, which is the default for Put and Delete

Numbers keep their full precision across the boundary, so a 19-digit identifier or an epoch-nanosecond timestamp survives the round trip exactly.