Design rate limiting and abuse protection for a public ASP.NET Core API used by external clients.

Design rate limiting and abuse protection for a public API

Designs layered public API protection with caller identity, quotas, burst limits, abuse signals, and client-friendly responses.

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I would identify callers by API key, client id, user, tenant, or IP depending on the API. Then I would define limits such as per-minute bursts, daily quotas, and expensive-operation limits. The API would return 429 with useful retry information when a limit is exceeded. I would start with observability and gradual rollout so real clients are not surprised by a hidden policy change.

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Caller identity, quota design, distributed enforcement, 429 responses, abuse detection, rollout, and monitoring.

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Rate limiting is more than blocking attackers. A good design protects platform capacity while giving legitimate clients predictable behavior.
I would identify callers by API key, client id, user, tenant, or IP depending on the API. Then I would define limits such as per-minute bursts, daily quotas, and expensive-operation limits. The API would return 429 with useful retry information when a limit is exceeded. I would start with observability and gradual rollout so real clients are not surprised by a hidden policy change.
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For distributed enforcement, I would use a shared store or gateway-level limiter rather than per-process counters only. Limits need scopes: anonymous traffic, authenticated users, tenants, partner clients, and internal service calls may need different policies. I would also protect high-cost endpoints separately because one search or export call may cost more than many simple reads. Clients need response headers, documentation, and a way to request higher quotas when business needs justify it.

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Counting only by IP when authenticated clients exist.
Using local memory counters in a scaled-out API.
Returning 429 without retry guidance.
Rolling out limits with no visibility into affected clients.

Design rate limiting and abuse protection for a public ASP.NET Core API used by external clients.

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