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crypto-exchange
crypto exchange with custody
Coinbase
System
Techniques · 17
Primitives · 78
crypto-exchange
Deterministic simulation testing
distributed · 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 replication
distributed · 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.
›
Margin liquidation
finance · medium: Mark-to-market margin calls and forced liquidation of under-margined positions, incl. insurance fund and auto-deleveraging
Matching engine
finance · medium: Single-threaded, deterministic loop that journals sequenced orders, matches them by price-time priority against a limit order book and emits trades.
›
Reorg safe chain indexing
finance · medium: Index blockchain events with confirmation depth, reorg rollback and finality tracking
Total order sequencer
finance · medium: Single sequencer stamps every inbound message so replicated deterministic state machines (LMAX style) replay identically
Coverage-guided fuzzing
security · medium: Mutate inputs, run an instrumented target, and keep any input that reaches a new code edge; feedback turns blind guessing into incremental search.
›
Double-entry ledger
finance · low: Append-only journal of transactions whose postings sum to zero per currency; balances are derived, so money can only move, never appear or vanish.
›
Money representation
finance · low: Store money as integer minor units with an explicit currency exponent, compute in wider integers, and round once with a named rounding mode.
›
Limit order book
finance · low: Per-symbol store of resting orders as FIFO queues per price level; array-indexed ticks plus intrusive lists give O(1) add, cancel and best-price lookup.
›
Idempotency keys
finance · low: Client-chosen unique key per logical operation, stored with a request fingerprint and the final response, so retries replay the first result instead of acting twice.
›
Dual control approval
security · low: Four-eyes / maker-checker approval with quorum policies for sensitive operations
ECDSA signatures
security · low: The elliptic-curve signature standardised in FIPS 186-5 (P-256) and used by secp256k1 ledgers; 64-byte signatures, but a repeated or biased nonce leaks the private key.
›
Hdr histogram
data-structures · low: Log-linear bucketed histograms with bounded relative error for latency percentiles
Event sourcing
finance · low: Persist state changes as an append-only stream of immutable events per entity; current state is a fold over them, guarded by expected-version appends.
›
Hierarchical deterministic keys
finance · low: BIP-32/39/44 seed phrases and child-key derivation paths for wallets
Pre-trade risk checks
finance · low: Constant-time gate in front of order entry that rejects fat-finger, over-limit and runaway orders using worst-case exposure counted over open orders.
›
Reconciliation
finance · low: Match internal ledger records against bank and processor statements by reference, then amount and date window; every unmatched or mismatched item becomes an exception.
›
Process supervision
hardware-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.
›
WebSockets
networking · low: Full-duplex message framing over one upgraded HTTP connection; the standard way to push real-time data to browsers.
›
Mutual TLS
security · low: TLS where the client also proves a certificate key, so every connection carries a verified, rotatable machine identity.
›
Graceful draining
systems · 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.
›
Token bucket
systems · low: A bucket of up to b tokens refilled at rate r; requests spend tokens, enforcing an average rate while allowing bursts of b.
›
+ 10 more techniques
+ 62 more primitives
System
Techniques · 17
Primitives · 78
crypto-exchange
Deterministic simulation testing
distributed · 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 replication
distributed · 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.
›
Margin liquidation
finance · medium: Mark-to-market margin calls and forced liquidation of under-margined positions, incl. insurance fund and auto-deleveraging
Matching engine
finance · medium: Single-threaded, deterministic loop that journals sequenced orders, matches them by price-time priority against a limit order book and emits trades.
›
Reorg safe chain indexing
finance · medium: Index blockchain events with confirmation depth, reorg rollback and finality tracking
Total order sequencer
finance · medium: Single sequencer stamps every inbound message so replicated deterministic state machines (LMAX style) replay identically
Coverage-guided fuzzing
security · medium: Mutate inputs, run an instrumented target, and keep any input that reaches a new code edge; feedback turns blind guessing into incremental search.
›
Hardware security module (HSM)
security · medium: A tamper-resistant device or service that generates keys, signs, decrypts and wraps with them internally, and releases a key only as ciphertext.
›
Mfa
security · medium: Multi-factor authentication flows: TOTP, push, WebAuthn second factor, recovery codes, step-up
Threshold ecdsa mpc
security · medium: Multi-party ECDSA signing (GG18/CMP-style) with presignatures and key refresh
Point-in-time recovery
storage · medium: Periodic base backups plus a continuously archived change log let you rebuild the state as of any instant, then branch from there.
›
Delta debugging
compilers · medium: Ddmin minimization of failing inputs or change sets
Fault injection
distributed · medium: Inject latency, errors, kills and partitions via proxies, netem or hooks
Homomorphic encryption
security · medium: Additively homomorphic ElGamal/Paillier for encrypted tallies and private aggregation
ARIES recovery
storage · medium: Three-pass crash recovery (analysis, redo, undo) for steal/no-force buffer pools; repeats history, then rolls back losers with compensation log records.
›
Syscall interception
security · medium: Intercept syscalls via ptrace, seccomp user notify or a user-space kernel
Buffer pool
storage · medium: The database's own page cache (frames, page table, pin counts, dirty bits, replacement) so it, not the OS, controls eviction, write order and I/O.
›
Double-entry ledger
finance · low: Append-only journal of transactions whose postings sum to zero per currency; balances are derived, so money can only move, never appear or vanish.
›
Money representation
finance · low: Store money as integer minor units with an explicit currency exponent, compute in wider integers, and round once with a named rounding mode.
›
Limit order book
finance · low: Per-symbol store of resting orders as FIFO queues per price level; array-indexed ticks plus intrusive lists give O(1) add, cancel and best-price lookup.
›
Idempotency keys
finance · low: Client-chosen unique key per logical operation, stored with a request fingerprint and the final response, so retries replay the first result instead of acting twice.
›
Dual control approval
security · low: Four-eyes / maker-checker approval with quorum policies for sensitive operations
ECDSA signatures
security · low: The elliptic-curve signature standardised in FIPS 186-5 (P-256) and used by secp256k1 ledgers; 64-byte signatures, but a repeated or biased nonce leaks the private key.
›
Hdr histogram
data-structures · low: Log-linear bucketed histograms with bounded relative error for latency percentiles
Event sourcing
finance · low: Persist state changes as an append-only stream of immutable events per entity; current state is a fold over them, guarded by expected-version appends.
›
Hierarchical deterministic keys
finance · low: BIP-32/39/44 seed phrases and child-key derivation paths for wallets
Pre-trade risk checks
finance · low: Constant-time gate in front of order entry that rejects fat-finger, over-limit and runaway orders using worst-case exposure counted over open orders.
›
Reconciliation
finance · low: Match internal ledger records against bank and processor statements by reference, then amount and date window; every unmatched or mismatched item becomes an exception.
›
Process supervision
hardware-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.
›
WebSockets
networking · low: Full-duplex message framing over one upgraded HTTP connection; the standard way to push real-time data to browsers.
›
Mutual TLS
security · low: TLS where the client also proves a certificate key, so every connection carries a verified, rotatable machine identity.
›
Graceful draining
systems · 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.
›
Token bucket
systems · low: A bucket of up to b tokens refilled at rate r; requests spend tokens, enforcing an average rate while allowing bursts of b.
›
Cooperative scheduling
concurrency · low: Green threads/coroutines yielding at await points on a user-space scheduler
Record replay
distributed · 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 rebuild
PRNGs (PCG, xoshiro)
numerics · low: Small, fast, statistically strong non-cryptographic generators: PCG32 and xoshiro256**, with seeding, parallel streams and unbiased ranges.
›
Leases
distributed · 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.
›
Write-ahead log
storage · low: Append each change to a checksummed sequential log and fsync it before touching data pages; the basis of crash durability in nearly every database.
›
Health checking
systems · low: Decide per backend whether to route to it using probes and real-traffic errors, with consecutive-count hysteresis, capped ejection and a panic fallback.
›
d-ary heap
data-structures · low: Array heap with d children per node (d = 4 typical): half the binary heap's depth, siblings in one cache line, faster priority queues.
›
Sequenced multicast feed
networking · low: Exchange order-by-order data as fixed binary messages in sequenced UDP multicast packets
Low-latency hot path
finance · low: Rules for microsecond trading paths: one pinned busy-polling thread per stage, no allocation, syscalls, locks or page faults after startup, kernel-bypass I/O, and measured tails.
›
Message sequence numbers
distributed · low: A per-stream counter on every message lets the receiver detect loss, duplicates and reordering, ack cheaply and resume after reconnect with "send from N".
›
Journaled state revert
storage · low: Undo journal of state writes enabling nested checkpoints and cheap revert
IP multicast
networking · low: Send each datagram once to a class D group address; the network copies it to every joined receiver, and sequence numbers let receivers find loss.
›
Gapless sequence numbers
storage · low: Gap-free, monotonic numbering (invoices, journal entries) under concurrency and rollbacks
Code coverage instrumentation
compilers · low: Insert counters into compiled code to record which blocks, edges or lines ran; a spanning tree of the control-flow graph cuts the counters needed.
›
Fast hash functions
data-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.
›
Sanitizers
security · low: ASan/UBSan/TSan shadow memory and instrumentation to catch memory bugs
Aes key wrap
security · low: AES Key Wrap (RFC 3394/5649) and AES-GCM-SIV for deterministic, authenticated wrapping of key material
Csprng
security · low: OS-backed cryptographically secure random numbers (getrandom), and when a fast PRNG is not enough
Secure memory zeroization
security · low: Keep secrets in one locked, fixed-size, non-copyable region, erase them with writes the compiler must keep, and exclude them from dumps and swap.
›
Passkeys (WebAuthn)
security · low: Phishing-resistant login with a per-site key pair held by the device or password manager; the server stores only a public key.
›
One-time codes (HOTP, TOTP)
security · low: Short numeric codes derived from a shared secret plus a counter or the clock (HOTP, TOTP), or random codes sent by SMS or email; safe only with expiry, single use and attempt limits.
›
Sliding-window counters
systems · low: Count events in the last W seconds with a ring of sub-bucket counters; the two-bucket weighted estimate gives rate limits in 16 bytes per key.
›
Commitment schemes
security · low: Hash and Pedersen commitments: hide a value now, bind to it, reveal later
Shamir secret sharing (k-of-n)
security · low: Split a secret into n shares so any k reconstruct it and any k-1 reveal nothing at all, using a random polynomial over a finite field.
›
Sigma protocols
security · low: Schnorr and Chaum-Pedersen proofs of knowledge, OR-proofs for ballot validity
Object storage
cloud · low: S3-compatible blob storage at cents per GB-month with 11 nines durability; pick by egress price, request price and latency, not by storage price alone.
›
Copy on write snapshots
storage · low: Point-in-time snapshots by sharing pages/extents and copying only on write
Failure bisection
search-sort · low: Binary search over commits, batches or inputs to isolate a failure
Transparent interception
networking · low: Redirect traffic to a local proxy (iptables TPROXY/REDIRECT, eBPF) without app changes
Big integer arithmetic
numerics · low: Multi-limb integer arithmetic (256-bit and up): carries, Karatsuba, Montgomery and Barrett reduction
Finite field arithmetic
numerics · low: Prime-field and extension-field arithmetic (Montgomery form, Goldilocks, BabyBear), vectorized
Number theoretic transform
numerics · low: FFT over finite fields for exact polynomial and big-integer multiplication
Ebpf
hardware-os · low: Verified in-kernel programs on hooks (kprobes, XDP, tc) with maps
Ptrace process control
hardware-os · low: Ptrace: attach, read and write registers and memory, single-step, intercept signals
Seccomp bpf
security · low: Syscall filtering with seccomp BPF programs
fsync, O_DSYNC and O_DIRECT
hardware-os · low: What fsync, fdatasync, O_DSYNC, O_DIRECT and F_FULLFSYNC really guarantee on Linux and macOS, and the exact call sequences for crash-safe files.
›
LRU and CLOCK
systems · 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-FIFO
systems · 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.
›
Control-flow graph
compilers · low: Split a linear instruction list into basic blocks and connect them by jumps; the graph every optimizer, SSA builder and dataflow pass walks.
›
False sharing
concurrency · low: Independent variables written by different cores on one cache line force the line to bounce between cores; pad or regroup hot data to fix it.
›
Memory ordering
concurrency · low: What Relaxed, Acquire, Release and SeqCst atomics actually guarantee, what they cost on x86 and ARM, and which one each pattern needs.
›
SPSC ring buffer
data-structures · low: Bounded wait-free queue for exactly one producer and one consumer thread, built from an array and two indices with acquire/release ordering.
›
Fencing tokens
distributed · low: A number that grows with every lock grant and is checked by the protected resource, so a paused ex-holder's late write is rejected.
›
Largest remainder rounding
finance · low: Splitting an amount into parts that sum exactly (largest remainder / Hamilton) for allocations, splits and prorations
BFS and DFS
graphs · low: The two basic graph traversals; BFS gives hop distances and levels, DFS gives discovery/finish order for cycles, components and topological order.
›
Minimum spanning tree
graphs · low: Cheapest set of edges connecting all vertices; Kruskal sorts edges and joins components with union-find, Prim grows one tree, Boruvka merges in parallel rounds.
›
Union-find
graphs · low: Disjoint-set forest with union by size and path compression; merges sets and answers same-set queries in effectively constant time.
›
CPU caches and the memory hierarchy
hardware-os · low: Sizes, line widths and latencies of L1/L2/L3/DRAM on modern x86 and Apple M-series, and the data-layout rules that follow from them.
›
CRC32C checksums
hardware-os · low: The Castagnoli CRC-32 with dedicated instructions on x86 (SSE4.2) and ARMv8. It is the standard fast integrity check for storage blocks, logs and network frames.
›
Huge pages
hardware-os · low: 2 MB/1 GB pages to cut TLB misses; THP vs explicit hugetlbfs
Numa aware allocation
hardware-os · low: Allocate memory and pin threads on the local NUMA node; first-touch and interleave policies
SIMD programming
hardware-os · low: Process 4-16 lanes per instruction with AVX2, AVX-512 or NEON via Rust std::arch, with runtime dispatch and a portable fallback.
›
Ebpf xdp
networking · low: EBPF programs at the XDP/tc hooks for in-kernel packet processing at line rate
Kernel-bypass networking
networking · low: User space (DPDK, AF_XDP) or an in-driver eBPF hook (XDP) handles packets straight from NIC rings, skipping sockets, for 10-40 Mpps per core.
›
Receive side scaling
networking · low: NIC hashing of flows to RX queues (RSS) and symmetric hashing for per-core processing
Sparse matrices (CSR)
numerics · low: Compressed sparse row stores only nonzeros as row pointers, column indices and values; SpMV streams them once, so it is memory-bandwidth bound.
›
Cryptographic hashes (SHA-2, BLAKE3)
security · low: Collision-resistant fingerprints of data; SHA-256 for interoperability, BLAKE3 for speed, HMAC/HKDF for keyed uses.
›
Hash join
storage · low: Build a hash table on the smaller input's join key and probe it with every row of the larger one; the linear-time workhorse for equi-joins.
›
Optimistic concurrency control
storage · low: Run transactions without locks, record what they read, and validate at commit that nothing changed; fastest when conflicts are rare.
›
Arena allocator
systems · low: Allocate by bumping a pointer through big chunks and free everything at once: a few instructions per allocation for objects sharing a lifetime.
›
Exponential backoff with jitter
systems · low: Retry after delays that grow geometrically and are randomized, so failed clients spread out instead of hammering a recovering service in synchronized waves.
›
Slab allocator
systems · low: Pre-carve pages into equal-size slots per size class with an in-place free list: O(1) alloc and free, no external fragmentation, cache-warm reuse.
›
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