System Design · Engineering Foundry challenge level: Intermediate

Durable Webhook Delivery Platform

Design reliable customer webhook delivery with retries, ordering choices, replay controls, and protection against unhealthy destinations.

All challengesSuggested practice time: 70 minutes

Original prompt

What you are building

Design a platform that accepts internal domain events and delivers signed webhooks to customer endpoints. Customers need delivery history and controlled replay. Explain delivery guarantees, retry scheduling, endpoint isolation, security, and operational recovery.

Engineering Foundry originalNo company association

Deliverables

Requirements and explicit delivery semantics.
Architecture and durable state transitions.
Subscription, attempt, and replay data model.
External management APIs and internal events.
Retry, backpressure, and endpoint isolation strategy.
Security, monitoring, and tradeoffs.

Constraints

Delivery is at least once; consumers may receive duplicates.
Payload signatures must support key rotation.
One unhealthy tenant endpoint must not block unrelated tenants.
Replay must be bounded and auditable.

Success criteria

Durability boundaries and state transitions are clear.
Duplicate delivery and ordering are handled explicitly.
Retry storms and toxic endpoints are contained.
Operators can understand and safely replay failed deliveries.

Suggested workflow

Choose delivery and ordering semantics.
Model one event through every durable state.
Design partitioning and retry scheduling.
Trace slow, failing, and malicious endpoints.
Add customer and operator observability.

Attempt before reveal

Build your deliverable independently.

Use the prompt, constraints, and workflow first. Guidance offers considerations and questions - not a canonical solution.

Reveal guidanceDirections and questions to test

Considerations

Separate immutable event payloads from mutable delivery attempts.
Use explicit idempotency identifiers even though the receiver controls its own deduplication.
Consider per-endpoint circuit breaking and fair scheduling across tenants.

Reveal common mistakesFailure patterns worth checking

Promising exactly-once delivery over HTTP.
Retrying every failure immediately.
Conflating event creation with delivery attempt state.
Providing unrestricted replay without audit or rate control.

Reveal stretch goalsOptional ways to extend the deliverable

Support payload transformation with safe versioning.
Design regional failover without reordering every stream.

Optional solution worksheet

Prepare your approach for discussion.

Capture your reasoning, then copy a plain-text summary you control.

Session only - not saved.Refreshing or leaving this page clears every worksheet field and self-review choice. Nothing is uploaded or officially submitted.

Approach summary

Key decision

Important tradeoff

Failure mode or edge case

Validation or testing plan

Reflection

Optional solution URLThis link remains in the current browser session and is included only if you copy the summary.

Nothing is sent when you copy.

Optional community discussion

Compare reasoning, not rankings.

Discuss this challenge in the Engineering Foundry community if you choose. Share your own work, explain assumptions, critique ideas rather than people, and remove confidential or proprietary material.

Discuss this challenge

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System Design · Engineering Foundry challenge level: Intermediate

Durable Webhook Delivery Platform

Design reliable customer webhook delivery with retries, ordering choices, replay controls, and protection against unhealthy destinations.

All challengesSuggested practice time: 70 minutes

Original prompt

What you are building

Engineering Foundry originalNo company association

Deliverables

Requirements and explicit delivery semantics.
Architecture and durable state transitions.
Subscription, attempt, and replay data model.
External management APIs and internal events.
Retry, backpressure, and endpoint isolation strategy.
Security, monitoring, and tradeoffs.

Constraints

Delivery is at least once; consumers may receive duplicates.
Payload signatures must support key rotation.
One unhealthy tenant endpoint must not block unrelated tenants.
Replay must be bounded and auditable.

Success criteria

Durability boundaries and state transitions are clear.
Duplicate delivery and ordering are handled explicitly.
Retry storms and toxic endpoints are contained.
Operators can understand and safely replay failed deliveries.

Suggested workflow

Choose delivery and ordering semantics.
Model one event through every durable state.
Design partitioning and retry scheduling.
Trace slow, failing, and malicious endpoints.
Add customer and operator observability.

Attempt before reveal

Build your deliverable independently.

Use the prompt, constraints, and workflow first. Guidance offers considerations and questions - not a canonical solution.

Reveal guidanceDirections and questions to test

Considerations

Separate immutable event payloads from mutable delivery attempts.
Use explicit idempotency identifiers even though the receiver controls its own deduplication.
Consider per-endpoint circuit breaking and fair scheduling across tenants.

Reveal common mistakesFailure patterns worth checking

Promising exactly-once delivery over HTTP.
Retrying every failure immediately.
Conflating event creation with delivery attempt state.
Providing unrestricted replay without audit or rate control.

Reveal stretch goalsOptional ways to extend the deliverable

Support payload transformation with safe versioning.
Design regional failover without reordering every stream.

Optional solution worksheet

Prepare your approach for discussion.

Capture your reasoning, then copy a plain-text summary you control.

Session only - not saved.Refreshing or leaving this page clears every worksheet field and self-review choice. Nothing is uploaded or officially submitted.

Approach summary

Key decision

Important tradeoff

Failure mode or edge case

Validation or testing plan

Reflection

Optional solution URLThis link remains in the current browser session and is included only if you copy the summary.

Nothing is sent when you copy.

Optional community discussion

Compare reasoning, not rankings.

Discuss this challenge

Durable Webhook Delivery Platform

What you are building

Deliverables

Constraints

Success criteria

Suggested workflow

Build your deliverable independently.

Considerations

System Design deliverable self-review

Prepare your approach for discussion.

Compare reasoning, not rankings.

Durable Webhook Delivery Platform

What you are building

Deliverables

Constraints

Success criteria

Suggested workflow

Build your deliverable independently.

Considerations

System Design deliverable self-review

Prepare your approach for discussion.

Compare reasoning, not rankings.