As previously communicated, we have begun requiring Project IDs with all JSONRPC requests. Requests without a project ID or requests using legacy keys will be heavily throttled at this time. If your application receives JSONRPC errors with the error message “legacy access request rate exceeded” you must upgrade your project to use Project IDs.
Please visit https://infura.io/dashboard to create and manage Project IDs to use with all requests going forward. See https://infura.io/docs/gettingStarted/makeRequests for details on using Project IDs with requests to Infura.