Resend is a developer-focused transactional email API. These exercises cover domain setup, React Email integration, delivery webhooks, batch sending, and idempotency — everything you need to build reliable email infrastructure.
0 / 5 completed
1 / 5
At standup, a colleague asks what Domains in Resend are used for. What is the correct answer?
A Domain in Resend is a verified sending domain. You add DNS records — DKIM (for email signing), SPF (for authorised senders), and optionally DMARC (for policy enforcement) — and Resend verifies the setup. Once verified, you can send from any address at that domain (e.g., hello@yourcompany.com) and benefit from Resend's sending infrastructure and improved deliverability.
2 / 5
During a PR review, a teammate asks how React Email integrates with Resend. Which answer is correct?
React Email lets you write email templates as React components with familiar JSX. You render a component to an HTML string using render(<MyEmail />) from @react-email/render and pass the result as the html parameter to resend.emails.send(). Resend does not render React server-side — you render locally and send the HTML string. This approach produces email-client-compatible HTML without writing inline styles manually.
3 / 5
In a design review, the team discusses email webhooks in Resend. What events can they deliver?
Resend webhooks push delivery lifecycle events to your endpoint via HTTP POST. Events include email.sent, email.delivered, email.delivery_delayed, email.bounced, email.complained (spam reports), and email.opened / email.clicked (with tracking enabled). Each event payload includes the email ID, recipient, and timestamp, letting you build delivery monitoring and bounce handling without polling.
4 / 5
An incident report shows duplicate transactional emails being sent during a retry storm. A senior engineer asks what idempotency support Resend provides. What is correct?
Resend supports the Idempotency-Key HTTP header. If you include a unique key (e.g., a UUID tied to your order ID) in your request, and a network failure causes you to retry, Resend detects the duplicate key and returns the original response without sending a second email. This prevents transactional emails from being sent multiple times during retry storms or at-least-once delivery retries.
5 / 5
During a code review, a senior engineer asks how batch send works in Resend. What is accurate?
Resend's resend.batch.send() method accepts an array of email objects, each fully specified with its own recipient, sender, subject, and content. Resend enqueues all emails in the batch and returns an array of { id } objects — one per email. This is more efficient than making multiple individual API calls and is useful for sending personalised transactional emails (order confirmations, notifications) to multiple recipients at once.