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cdn

content delivery network

Cloudflare, Akamai

SystemTechniques · 17Primitives · 65 cdn Deterministic simulation testingdistributed · medium: Run the whole system in one thread under a seeded scheduler with simulated network, disk and clock, so every failure replays from its seed.›Primary-backup replicationdistributed · medium: One node orders all writes and ships them to standbys; the acknowledgement rule (none, one, all) sets what a crash loses, and an external arbiter decides who takes over.›QUICnetworking · medium: Encrypted, multiplexed transport over UDP with 1-RTT setup, independent streams and connection migration; the transport of HTTP/3.›Coverage-guided fuzzingsecurity · medium: Mutate inputs, run an instrumented target, and keep any input that reaches a new code edge; feedback turns blind guessing into incremental search.›TLS 1.3security · medium: The standard encrypted, authenticated transport; one round trip, only forward-secret AEAD suites, and little left to misconfigure.›Tls terminationsecurity · medium: Terminate TLS at a proxy: SNI cert selection, session resumption, OCSP, kTLS offload (listed in Moved to the wiki)Log-structured storagestorage · medium: Make the log the store: append every write, point an index at the newest copy, reclaim space by copying live records forward.›BBR congestion controlnetworking · low: Model-based congestion control that paces at the measured bottleneck bandwidth and caps inflight near one BDP, instead of reacting to loss.›LRU and CLOCKsystems · low: LRU evicts the least recently used entry via hash map plus linked list; CLOCK approximates it with a reference bit, so hits take no lock.›S3-FIFOsystems · low: Three FIFO queues (small, main, ghost) that evict one-hit wonders quickly and keep reused objects; low miss ratios with no list moves on hits.›Zstandard (zstd)compression · low: LZ77 plus Huffman and FSE entropy coding, with levels from LZ4-like speed to xz-like ratio, all decoding at about 1-2 GB/s.›Hdr histogramdata-structures · low: Log-linear bucketed histograms with bounded relative error for latency percentilesConsistent hashingdistributed · low: Hash nodes and keys onto a ring; each key belongs to the next node clockwise, so membership changes move only about 1/n of keys.›Process supervisionhardware-os · low: A parent process starts services, reaps their exits and restarts them under a delay and burst-limit policy, then stops them with SIGTERM before SIGKILL.›Anycastnetworking · low: Announce one IP prefix from many sites over BGP; routing sends each client to its preferred site, and a failed site leaves by withdrawing the route.›HTTP/2networking · low: Binary multiplexed framing for HTTP over one TCP connection: streams, per-stream and per-connection credit windows, HPACK header compression and the limits that contain abuse.›HTTP caching semanticsnetworking · low: The rules (RFC 9111) that decide whether a stored response is still fresh, and how a cheap conditional request revalidates it when it is not.›Maglev hashingnetworking · low: Consistent hashing into a fixed prime-size lookup table filled by per-backend permutations; O(1) lookups, near-perfect balance, little disruption on backend changes.›Zero-copy I/Onetworking · low: Move bytes between files, sockets and NICs by passing page references instead of copying through user space: sendfile, splice, MSG_ZEROCOPY, kTLS.›Hmac request signingsecurity · low: HMAC canonical-request signatures and presigned URLs (SigV4 style) with expiryMutual TLSsecurity · low: TLS where the client also proves a certificate key, so every connection carries a verified, rotatable machine identity.›Graceful drainingsystems · low: On a termination signal, stop taking new work, finish in-flight work until a deadline, tell clients to reconnect elsewhere, then exit; clients resume from a token.›Origin shieldingsystems · low: Route cache misses through one intermediate tier to cut origin load+ 10 more techniques+ 49 more primitives

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