I Moved My Prompts Into DynamoDB and the Throttling Went Away

Prompts can feel like configuration, so it's easy to store them in a managed prompt-management service that provides versioning, a console, and a clean API. However, this approach can lead to issues under load when prompt retrieval sits on the hot path of every inference call and the service starts throttling requests. The throttling becomes a ceiling on the whole pipeline, with the model not being the bottleneck.

The source of truth for prompts should be a managed service that handles authoring and governance, but it should not be the hot path for prompt retrieval. DynamoDB is an ideal choice for this access pattern because it excels at single-item reads by primary key, and its read throughput scales with the table, not a fixed service quota. Read latency is predictable, typically falling in the single-digit millisecond range.

To keep the cache honest and ensure that the serving copy is always up-to-date, the author recommends using a checksum-based sync. The managed service remains the source of truth for prompt content, while DynamoDB holds the serving copy that the hot path reads. A checksum is computed for each prompt in the source of truth, and it is compared against the checksum stored in DynamoDB.

If the checksums match, no action is taken; if they differ, the prompt has changed, and the new content is written into DynamoDB. This approach ensures that only genuine edits at the source trigger a write, minimizing unnecessary writes.

The migration process is straightforward. The table is modeled around the lookup, with the partition key set to the prompt identifier. This schema is sufficient if a single current copy per prompt is all that is needed. However, if history, rollback, or audit trails are required, a version can be added to the key as the sort key.

A monotonic integer, ISO timestamp, or the checksum itself can be used as the version. The hot path reads the current pointer by key, ensuring that serving remains a single keyed read. History can be queried with a Query on the partition key, while the checksum still dictates when a new version row is written, preventing unnecessary writes for unchanged prompts.

The tradeoff between the single-copy layout and the versioned layout is simple. The single-copy layout is less to manage, while the versioned layout provides rollback and audit capabilities. Both approaches are key reads on the hot path, so they do not reintroduce the throttling problem. In summary, the migration to DynamoDB for prompt serving was small yet effective, ensuring that prompt retrieval no longer becomes a shared, rate-limited dependency and becomes a key read operation.