Amazon EventBridge vs Upstash QStash

Amazon EventBridge

IAM policies scope a credential to single actions and buses, and an SLA commits 99.99 per cent monthly uptime per Region. The Custom Event Bus API of 24 September 2026 adds retention, replay, ordering and publish-time deduplication. Classic PutEvents takes no idempotency token and answers 200 for a bus that does not exist. A person must open the AWS account.

Upstash QStash

A public OpenAPI 3.1 file covers 43 operations, and publishing has no per-second limit, deduplication IDs and a dead letter queue with replay. Each region has one full-access token and one read-only token, and the token may travel in the URL. The Markdown pricing page contradicts itself on whether retries are billed.

Amazon EventBridge

1. Use aws eventsv2 and the EventBridgeV2 SDK client for the Custom Event Bus, but write IAM actions with the events: prefix. A policy naming eventsv2: grants nothing
2. After a Classic PutEvents call, check FailedEntryCount and each entry's ErrorCode, then resend failed entries yourself. A request holds up to 10 entries and under 1 MB
3. Set SystemMetadata.DeduplicationId on Custom Event Bus entries when retrying a publish, and treat a SuccessCode of DEDUPLICATED as success
4. Set RetryPolicy and OnFailureConfiguration when creating a subscriber. The defaults stop after 5 attempts or 300 seconds, and an exhausted event is dropped
5. Store the full bus ARN. A Custom Event Bus ARN ends in a generated identifier that changes when a bus of the same name is recreated

Upstash QStash

1. Use the regional host that matches the token. qstash.upstash.io is the EU region, and US tokens work only on qstash-us-east-1.upstash.io
2. Send Upstash-Deduplication-Id on every publish so a retried request isn't queued twice. The window is 10 minutes
3. Budget for retries. Per the pricing FAQ each delivery attempt is billed as a message, so set Upstash-Retries deliberately
4. Give monitoring agents the read-only token, and set Upstash-Redact-Fields on publish, because that token still reads message bodies and headers
5. Make the destination idempotent on Upstash-Message-Id. Delivery is at least once, and duplicates can follow a server restart