Neptune vs DynamoDB for Graph-Shaped Data
Amazon Neptune is built for graph data, but DynamoDB can model nodes and edges too, and the right choice depends on your queries, budget, and setup time. This compares the two on traversal, cost, free tier, and effort, with a simple guide to choosing between them.
Amazon Neptune, a purpose-built graph database, or DynamoDB with a graph-friendly schema. I'm working through this choice on a project right now, so this is an evaluation based on AWS's own docs and pricing rather than a long-running production verdict.
The short version
| Neptune | DynamoDB | |
|---|---|---|
| Built for graphs | Yes | No, but has a documented pattern for it |
| Query languages | Gremlin, openCypher, SPARQL | Key and index lookups |
| Multi-hop traversal | One query | Repeated queries from your code |
| Cost when idle | Always-on capacity | Close to nothing |
| Free tier | 30-day trial only | Always-free allowance |
| Setup effort | Higher | Lower |
Neptune: the right tool, with real overheads
Neptune is built for connected data. You can ask "everything within three hops of this node" as a single query rather than assembling it yourself, and it supports both property graph and RDF models.
The costs are practical rather than technical. Neptune Serverless can scale down to 1 NCU, but that still means paying for capacity while nothing is happening, and one third-party estimate puts that floor at roughly $80 a month in US East, so check the current pricing page before relying on it. I/O charges under standard pricing can also become the main cost for traversal-heavy workloads, which is what the I/O-Optimized option exists to address. On top of that, the cluster sits inside a VPC, so anything calling it, including a Lambda function, needs the networking set up first.
DynamoDB: graph-shaped, not graph-native
AWS documents the adjacency list pattern as a way to represent graph data in DynamoDB. Relationships are stored as their own items, and a global secondary index on the sort key lets you look them up in the reverse direction too.
That works well for one-hop questions: "what is this connected to, and which way". It gets awkward beyond that. DynamoDB has no joins and no traversal, so each extra hop is another round trip from your own code, and variable-depth questions mean writing the traversal logic yourself. What you get in return is a service with an always-free allowance, no idle capacity charge, and nothing extra to learn if you already use it.
How I'm thinking about the choice
If you start on DynamoDB, a few habits keep a later move to Neptune a port rather than a rebuild: stable entity IDs, edges stored as their own items with a type and direction, and properties on the edge when they describe the relationship.
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