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distributed-sql

globally distributed SQL database

Spanner, CockroachDB

SystemTechniques · 31Primitives · 73 distributed-sql Clock synchronizationdistributed · medium: Estimate a clock's offset from four timestamps, filter out queueing noise, and steer the clock smoothly; NTP gets about a millisecond, PTP with hardware timestamps under a microsecond.›Data shuffledistributed · medium: Hash/range repartitioning of intermediate data between workers (exchange operator)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.›Multi raftdistributed · medium: Thousands of Raft groups per node: batched heartbeats, shared log engine, range split/mergePrimary-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.›Raftdistributed · medium: Leader-based consensus on a replicated log; one leader per term, majority commit; the default for a strongly consistent replicated state machine.›SWIM gossip membershipdistributed · medium: Each node probes one random peer per period, asks k others on timeout, and piggybacks membership updates; constant load per node at any cluster size.›Range partitioningdistributed · low: Cut the sorted key space into contiguous half-open ranges kept in a boundary map; split hot or big ranges, merge small ones, move ranges between nodes.›Leasesdistributed · low: A lock that expires on its own: bounded-time ownership that survives crashes and partitions, given bounded clock drift and fencing tokens on writes.›Bloom filterdata-structures · low: Bit array answering "definitely not present" or "probably present" in about 10 bits per key for 1 % false positives; inserts are cheap, deletes impossible.›Hdr histogramdata-structures · low: Log-linear bucketed histograms with bounded relative error for latency percentilesHybrid logical clocksdistributed · low: A 64-bit timestamp that tracks wall-clock time but never goes backwards and respects causality; the default timestamp for MVCC databases without atomic clocks.›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.›Mutual 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.›PID controllerrobotics · low: Drive a measured value to a setpoint with three terms on the error: proportional, integral, derivative. The default feedback loop for motors, heaters, drones and gimbals.›Phase-locked loop (digital)signal-processing · low: Feedback loop that locks a local oscillator to the phase and frequency of an input tone; the core of carrier recovery, clock recovery and GNSS tracking.›Robust statisticsstatistics · low: Location and scale estimates (median, MAD, trimmed mean, Huber M-estimator) that stay correct when a minority of the data is garbage.›Fast hash functionsdata-structures · low: Non-cryptographic hashes built from 64×64→128-bit multiplies and xor-shifts; pick by key size, trust level and whether the hash is persisted.›Columnar memory formatstorage · low: In-memory column buffers with validity bitmaps and offsets (Arrow style) for zero-copy exchangeCooperative schedulingconcurrency · low: Green threads/coroutines yielding at await points on a user-space schedulerRecord replaydistributed · low: Record every nondeterministic input (time, randomness, I/O, model and tool outputs, per-tick player input) and re-execute deterministically for debugging, replays and state rebuildPRNGs (PCG, xoshiro)numerics · low: Small, fast, statistically strong non-cryptographic generators: PCG32 and xoshiro256**, with seeding, parallel streams and unbiased ranges.›+ 24 more techniques+ 57 more primitives

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