Contents
All 52 chapters of How Data Works, in 8 parts. 243,471 words.
Every chapter
- 1The Whole Data System in One LookBy the end of this chapter, you should be able to follow one sale from a person’s action to a stored record and then to a report. You should also be able…application · database · dbms · invariant · observation · validation · evidence · reconciliation · file format · interface · sql · concurrency · query · derived data · grain · cardinality · transaction · commit · rollback · durability · model · contract · implementation detail · reproducible example21 min
- 2What a Record Really MeansThis chapter teaches you to look at a record and ask the questions that a screen full of neat columns can hide. What is being claimed? What does one row…field · domain · syntax · semantics · schema · schema version · parser · coercion · grain · aggregation · functional dependency · historical value · identifier · composite key · namespace · deduplication · event time · recording time · provenance · lineage · revision · correction · audit trail · retention20 min
- 3Numbers, Text, Time and Missing ValuesA database cannot make a field meaningful if the application has chosen the wrong kind of value. This chapter explains the everyday decisions hidden…type · domain type · storage type · lossy conversion · integer · range · overflow · scale · floating point · decimal arithmetic · quantisation · rounding policy · code point · encoding · grapheme cluster · normalisation · date · instant · utc offset · duration · null · empty string · denominator · missingness policy22 min
- 4Measurements, Units and UncertaintyYou will turn “we measured it” into a statement that names the object, quantity, unit, method and time. You will convert units without accidentally…measurand · indication · gross mass · tare mass · unit · conversion factor · dimension · dimensional analysis · precision · accuracy · sample standard deviation · resolution · calibration · rounding · half-even · quantisation · significant figures · target population · sampling frame · selection bias · censored observation · standard uncertainty · combined standard uncertainty · expanded uncertainty · covariance · uncertainty budget27 min
- 5Identity, Keys and the Problem of DuplicatesYou will distinguish a thing, its record, its display name and the identifier used to refer to it. You will choose a key by examining its scope and…entity · identifier · display name · primary key · natural key · surrogate key · unique constraint · uuid · namespace · composite key · foreign key · tenant scope · event identity · delivery attempt · idempotency · deduplication · identity conflict · entity resolution · candidate match · precision, matching · recall · false positive · canonical id · crosswalk · merge decision · split · identity history27 min
- 6From Events to State: Keeping HistoryYou will distinguish a record of something happening from a value describing the current position. You will reconstruct a notebook stock figure without…state · event · projection · event sourcing · observation · stock adjustment · command · state transition · expected version · stale request · invariant · authorisation · stream sequence · causal order · logical clock · partial order · sequence gap · commutative operation · snapshot · checkpoint · deterministic replay · materialised projection · projection version · side effect · reversal · compensation · replacement entry · correction target · reconciliation · append-only · retention boundary · reconstruction boundary · data minimisation · integrity check · restoration33 min
- 7Files, Folders and Data FormatsYou will separate the location of a file from the identity of its contents and the identity of the records inside it. You will follow bytes through…path · relative path · file extension · content digest · capture boundary · provenance · decoding · parsing · framing · length prefix · truncation · syntactic validity · csv · delimiter · quoting · dialect · logical record · import profile · json object · json array · duplicate member · deserialisation · schema version · unknown field · binary format · byte order · magic marker · envelope · compatibility · column-oriented format · quarantine · candidate · reconciliation · file-level error · conflict group36 min
- 8Why Databases ExistYou will explain the shared-file problem without claiming that ordinary files are useless. You will distinguish stored data, a database engine and the…lost update · read-modify-write · invariant · coordination boundary · busy outcome · partial operation · database engine · dbms · query · query plan · metadata · bound parameter · embedded database · client-server database · connection · connection pool · process boundary · serverless, in sqlite · transaction · commit · rollback · atomicity · isolation · durability · backup · restore test · recovery point objective · recovery time objective · migration · recovery unit · workload · contention · authoritative representation · portability · operational owner35 min
- 9Tables, Rows and RelationshipsYou will describe a table as a collection of claims with a defined row meaning, not merely a grid of cells. You will distinguish a column’s storage type…table · row grain · tuple · projection, in a query · multiset · distinct · column · domain · coercion · not null · check constraint · destination capacity rule · foreign key · parent row · child row · cardinality · one-to-many · one-to-one · many-to-many · junction table · composite key · join · fan-out · existence test · optional relationship · nullable foreign key · inner join · left join · sentinel entity · result population · agreed line price · catalogue price · referential integrity · publication unit · schema boundary35 min
- 10Designing a Schema That Matches the WorkYou will turn a description of somebody’s work into a small set of records with explicit meanings. You will separate the question “what do people need to…schema design · workflow · precondition · postcondition · write path · identity boundary · grain contract · participation minimum · flattened export · temporal interpretation · current attribute · historical snapshot attribute · draft record · repricing · mutation policy · business domain · storage type · lossless coercion · pre-binding validation · arithmetic bound · data dictionary · namespace · qualified name · system metadata · result contract · counterexample · traceability matrix · model defect · enforcement gap · evidence gap36 min
- 11Constraints: Rules the Database Can EnforceYou will explain a constraint as an enforced acceptance rule, not merely a note beside a field. You will distinguish a required value from a check on…constraint · not-null rule · check predicate · unknown result · boundary test · unique constraint · candidate key · primary key · key collision · existence precheck · foreign key · composite reference · referential action · half-specified reference · orphan row · invariant · cross-row invariant · detection versus prevention · authoritative counter · coordination boundary · immediate constraint · deferred constraint · commit-time failure · transaction ownership · repair branch · statement rollback · transaction rollback · constraint validation · schema migration · extended error code36 min
- 12SQL From Zero: Asking Your First QuestionsYou will read a small SELECT statement as a question about named records rather than a mysterious command. You will choose explicit output columns and…select statement · select list · text literal · cursor · declarative query · where predicate · three-valued logic · is null · operator precedence · inclusive interval · order by · tie-breaker · deterministic result order · limit · pagination · sql expression · alias · case expression · coalesce · integer division · insert · update · delete · target cardinality · wrong-scope mutation · bound parameter · placeholder · allowlisted query choice · guarded update · aba pattern · optimistic concurrency check37 min
- 13Joins and Normalisation: Putting Facts in the Right PlaceYou can now create tables and ask questions of one table. This chapter explains how to divide information between tables without losing its meaning, and…facts · repeat · joining · meaning · inner · outer · joins · functional · dependencies · normal · forms · trade-offs · avoiding · accidental · redundancy · update anomaly · historical snapshot · join predicate · composite key · cardinality · inner join · left outer join · null extension · functional dependency · attribute closure · lossless decomposition · prime attribute · normal form · denormalisation · fan-out · pre-aggregation · reconciliation24 min
- 14Scanning, Sorting and the Cost of a QuestionA query can return one number after examining millions of records. Another can return hundreds of records after examining only a small region of an…scan · width · data · volume · sorting · memory · external · work · spill · selectivity · filtering · cost · versus · elapsed · predicate · result cardinality · row width · projection · payload · sort key · tie-breaker · top-n · sorted run · merge fan-in · skew · residual filter · planner cost · elapsed time · queueing delay21 min
- 15Indexes: Building a Faster Way to Find ThingsAn index is an extra structure maintained to support particular ways of finding records. It is not a switch that makes every database operation faster.…extra · access · path · read · benefits · write · costs · composite · order · covering · partial · indexes · selectivity · distribution · index · access method · secondary index · write amplification · index maintenance · workload mix · composite index · leading key · lexicographic order · covering index · partial index · included column · locality · frequent value · workload envelope · eligible access path · plan selection · plan regression21 min
- 16B-Trees: Ordered Pages, Fast LookupsYou will build a small ordered tree by hand, follow a key from its root to a leaf, split a full page, and read a range across neighbouring leaves. The…ordered · separators · pages · fan-out · search · root · leaf · inserts · splits · range · scans · implementation · boundaries · separator key · occupancy · tree height · search invariant · record locator · membership check · page split · split propagation · key conservation · range scan · half-open interval · successor link · latch · oracle · structural validation20 min
- 17Hashing, Search Keys and CollisionsHashing maps an input to a value that can help organise or check data. The same word appears in hash tables, file digests, partition routing and security…deterministic · mapping · buckets · collisions · hash · tables · equality · cryptographic · non-cryptographic · purposes · distribution · adversarial · inputs · hashing · hash function · digest · framing · collision · load factor · probe sequence · equality contract · expected complexity · lossy index entry · preimage resistance · collision resistance · message authentication code · birthday effect · adversarial input · uniform model · false positive · content addressing · hash partitioning20 min
- 18Query Plans and the OptimiserA query states the answer required; a plan describes a way to obtain it. You will read that plan as a flow of records, estimates and operations rather…plan · statistics · estimates · join · strategies · access-path · choices · reading · explain · safe · intervention · execution plan · query rewrite · materialisation · histogram · cardinality estimate · correlation · nested-loop join · hash join · merge join · startup cost · blocking operation · path property · instrumentation · loop count · buffer hit · baseline · hypothesis-driven tuning · regression envelope17 min
- 19Aggregation, Windows and Useful ReportsA report is a calculation over a defined population. Its title, denominator and treatment of missing data matter as much as its SQL syntax. You will move…groups · grain · counts · sums · averages · windows · versus · time · buckets · distinctness · duplicates · reconciliation · totals · grouping key · report grain · aggregate state · denominator · weighted mean · known subtotal · window function · peer group · window frame · time bucket · as-of time · late arrival · distinct count · deduplication key · mergeable summary · contribution identity · exclusion register · transformation version16 min
- 20Measuring Performance Without Fooling YourselfA performance result is an observation about a defined workload, environment and measurement boundary. Without those definitions, a fast number can be…define · workload · latency · distributions · throughput · saturation · warm · versus · cold · state · fair · comparisons · reporting · limitations · benchmark contract · closed-loop load · open-loop load · percentile · tail latency · censored observation · backpressure · warm state · reset scope · counterbalancing · estimand · harness overhead · correctness oracle · raw sample · measurement boundary · external validity16 min
- 21Transactions: One Change, All or NothingA useful business action can require several database changes. This chapter explains how to give those changes one commit boundary without pretending…boundary · change · commit · rollback · atomicity · consistency · isolation · durability · savepoints · external · effects · outside · transaction · transaction boundary · business precondition · transaction owner · indeterminate outcome · invariant · failure domain · savepoint · partial rollback · outer transaction · external effect · outbox · compensation16 min
- 22Two People Change the Same RecordA program can be correct when run alone and wrong when another program changes the same facts between its steps. This chapter teaches you to write down…interleaving · actions · lost · updates · conditional · writes · uniqueness · under · competition · read-modify-write · traps · stock-reservation · case · race condition · schedule evidence · lost update · relative update · stale read · conditional write · affected-row check · complete scope · check-then-insert race · composite uniqueness · conflict policy · cross-row invariant · shared guard record · mutation path · reservation · unknown outcome · reconciliation18 min
- 23Isolation Levels and What You Can ObserveA transaction needs an answer to a deceptively simple question: which changes made by other transactions may it see? Isolation levels describe parts of…visibility · rules · statement · transaction · snapshots · non-repeatable · reads · write · skew · serialisable · execution · retries · operational · cost · isolation level · dirty read · phantom · statement snapshot · transaction snapshot · snapshot establishment · non-repeatable read · mixed-snapshot calculation · observation contract · write skew · read dependency · serializable outcome · serializability · serialization failure · predicate tracking · full-transaction retry · attempt amplification · retry deadline17 min
- 24Locks, Deadlocks and Safe RetriesA lock is a coordination mechanism, not a synonym for failure. Waiting can be the correct way to protect a record; waiting forever or repeating the wrong…locked · lock · modes · duration · blocking · versus · deadlock · detection · ordering · bounded · retries · avoiding · repeated · external · lock scope · lock holder · advisory lock · lock compatibility · lock lifetime · idle in transaction · wait-for graph · acquisition order · lock upgrade · deadlock victim · backoff · jitter · retry budget · external effect · outbox · delivery gap17 min
- 25Versions, Snapshots and Optimistic ConcurrencyA record can have more than one relevant version: the engine’s internal versions, a saved business revision and the copy someone is editing on a screen.…versions · snapshot · visibility · cleanup · long · readers · version · columns · compare-and-set · choosing · conflict · policy · mvcc · business revision · physical row location · visible version · edit precondition · stale client copy · obsolete version · vacuuming · cleanup horizon · version column · generation identifier · revision exhaustion · aba problem · optimistic concurrency · conflict resolution · merge granularity · last-write-wins policy17 min
- 26Invariants, Idempotency and the OutboxA reliable operation must survive more than a clean first attempt. Requests can arrive twice, replies can disappear, and external delivery can fail after…rules · across · operations · request · identity · replay · detection · atomic · intent · recording · outbox · delivery · consumers · end-to-end · invariant · state transition · reconciliation identity · request identity · payload equivalence · identity scope · incompatible key reuse · deduplication horizon · atomic intent recording · dual-write gap · dispatcher · inbox record · at-least-once delivery · acknowledgement boundary · end-to-end boundary · outcome reconciliation · scoped guarantee17 min
- 27Pages, Buffers and the Storage EngineSQL describes logical records, but a storage engine moves and manages physical units. This chapter connects rows to pages, memory buffers, free space and…logical · rows · physical · pages · buffer · pools · layout · dirty · flushing · free · space · fragmentation · reading · engine-specific · database page · slot entry · page occupancy · buffer pool · cache hit · eviction · row header · alignment · out-of-line value · dirty page · flush · redo · reusable space · rebuild · storage observation · freelist · runtime provenance17 min
- 28Write-Ahead Logs and RecoveryA crash can erase memory while leaving only part of the recent work in storage. Recovery needs a protocol for deciding what those surviving bytes mean.…recovery · information · exists · data · sequence · positions · checkpoints · redo · rollback · concepts · crash-recovery · traces · recovery log · log tail · recovery protocol · write-ahead ordering · group commit · asynchronous commit · log sequence number · durable prefix · replay position · checkpoint · redo horizon · checkpoint pressure · after-value · undo information · recovery base · crash trace · fault model · recovery target16 min
- 29LSM Trees and CompactionSome storage engines accept new writes into memory and later produce sorted immutable files instead of continually updating one in-place search tree.…sequential · writes · memory · tables · immutable · files · sorted · runs · read · amplification · compaction · tombstones · workload · trade-offs · lsm tree · write amplification · sorted run · memtable · immutable table file · manifest · merge iterator · visible sequence limit · run overlap · read amplification · negative lookup · filter false positive · tombstone · resurrection · compaction backlog · steady state · space amplification16 min
- 30Durability From Application to Device“Saved” can mean copied into an application buffer, accepted by the operating system, acknowledged by a storage device or preserved across a specified…acknowledgement · chain · process · memory · operating-system · caches · flush · requests · device · promises · failure · domains · testing · durability · acknowledgement chain · success boundary · durability contract · user-space buffer · page cache · partial write · file synchronization · directory durability · atomic visibility · volatile write cache · torn page · power-loss protection · failure domain · correlated failure · recovery dependency · failure injection · recovery oracle · durability evidence16 min
- 31Backups, Restore and Point-in-Time RecoveryA backup is a copy kept for a recovery purpose. Its value depends on whether the required state can actually be restored, validated and made usable…copies · recovery · purpose · consistent · snapshots · retention · objectives · restore · rehearsals · access · backups · backup · logical backup · physical backup · consistent backup boundary · application consistency · restore isolation · point-in-time recovery · archive coverage · recovery timeline · rpo · rto · restore rehearsal · backup verification · restore acceptance · replay review · backup retention · key dependency · restore-time suppression15 min
- 32Corruption, Reconciliation and RepairA wrong answer can come from damaged bytes, an invalid relationship, a faulty query, a mistaken business entry or a misunderstanding of the report. These…detecting · disagreement · checksums · limits · structural · checks · business · reconciliation · evidence-preserving · repair · incident · follow-through · physical corruption · logical inconsistency · checksum coverage · trusted expected digest · authentication · structural integrity check · referential check · checker scope · business reconciliation · authoritative field source · offsetting errors · preimage · repair manifest · evidence-preserving repair · containment · regression fixture · downstream impact15 min
- 33Replication: More Than One CopyA second copy of a database can help answer questions, survive some failures or move data closer to readers. It also creates a new question: which copy…copies · exist · physical · logical · approaches · synchronous · asynchronous · paths · staleness · read · routing · replication · restore · plan · replica · read scaling · failure domain · physical replication · logical replication · replication identity · asynchronous replication · synchronous acknowledgement · apply position · replication lag · stale read · catch-up rate · read-your-writes · monotonic reads · causal token · promotion · historical recovery point · recovery rehearsal17 min
- 34Leaders, Followers and FailoverA leader is not simply the machine with the newest-looking screen. It is a participant currently authorized by a defined protocol to coordinate…write · authority · failure · suspicion · election · promotion · fencing · stale · writers · lost · acknowledgements · safe · return · former · leader · control plane · data plane · heartbeat · failure suspicion · false suspicion · candidate eligibility · degraded redundancy · epoch · sequencer · unknown outcome · operation reconciliation · retry horizon · divergent history · reinitialization · failover runbook16 min
- 35Partitioning: Dividing the WorkPartitioning divides a collection into pieces. It can make some operations smaller, distribute capacity or align storage with the way records are…partition · keys · range · hash · approaches · partitions · rebalancing · cross-partition · questions · growth · permanent · shortcuts · partition key · locality · shard · range partition · hash partition · layout version · hot partition · skew · single-key contention · cutover · catch-up suffix · scatter-gather · partial aggregation · global invariant · indirection · consistent hashing · placement invariant16 min
- 36Consistency, Availability and Network Partitions“The system is consistent” is incomplete unless we state which observations are allowed. A database can obey its local constraints while different…name · consistency · model · availability · promises · partitioned · communication · precise · definitions · quorum · reasoning · limits · application-level · consequences · linearizability · sequential consistency · causal consistency · theoretical availability · service-level indicator · degraded mode · network partition · asymmetric failure · membership configuration · cap theorem · indistinguishable histories · consistency downgrade · quorum intersection · sloppy quorum · operation contract · authoritative outcome · allowed history16 min
- 37Consensus: Agreeing Despite FailureConsensus helps participants agree on a decision despite specified failures. In a replicated-log system, the decisions determine which commands occupy…agreement · problem · logs · terms · majorities · leader · changes · safety · progress · reading · consensus · trace · replicated state machine · committed prefix · term · log index · log matching · majority · voting restriction · current-term commitment · leader completeness · no-op entry · speculative suffix · liveness · byzantine behaviour · consensus trace · invariant check · commit eligibility16 min
- 38Distributed Transactions and SagasA local transaction can protect changes inside one database boundary. A workflow touching several independent resources needs an additional agreement or…transaction · across · participants · prepare · commit · in-doubt · work · compensation · saga · state · retries · choosing · explicit · failure · participant · coordinator · atomic commitment · two-phase commit · decision record · in-doubt transaction · blocking · heuristic resolution · semantic reversal · workflow state · orchestration · choreography · failure policy · intermediate state · recovery ownership16 min
- 39Caches, Queues and What They Do Not GuaranteeCaches reduce repeated work by keeping derived copies. Queues separate the arrival of work from its processing. Both can improve a system while also…derived · copies · invalidation · expiry · queue · acknowledgement · redelivery · order · backpressure · end-to-end · correctness · cache · cache hit · cache-aside · time to live · stale refill · publisher confirm · consumer acknowledgement · inbox record · completion order · per-entity ordering · prefetch · queue age · end-to-end correctness · boundary evidence · dead-letter disposition16 min
- 40Data Pipelines: Capture, Transform and DeliverA data pipeline carries information from one representation or system into another. It may copy, validate, reshape or summarise the records, but it must…sources · contracts · batch · extraction · change · capture · transformations · delivery · checkpoints · reconciliation · replay · data contract · provenance · transformation version · extraction boundary · consistent cut · incremental extraction · change data capture · snapshot-to-stream handover · replication slot · deterministic transformation · lossy transformation · output grain · checkpoint · atomic publication · replay-safe delivery · contiguous progress · reprocessing18 min
- 41Streams, Event Time and Late ArrivalsA stream keeps bringing records while a question is being answered. There may be no natural final record telling the system that a day’s information is…continuous · records · event · processing · time · windows · watermarks · late · corrections · state · checkpoints · replay · stream · unbounded input · partition progress · event time · processing time · ingestion time · window · sliding window · session window · watermark · late data · idle input · trigger · replacement result · allowed lateness · operator state · state checkpoint · restatement17 min
- 42Warehouses, Lakes and Analytical TablesThe database that accepts one customer’s order and the system that studies five years of orders solve different workloads. They may share data, but they…operational · versus · analytical · work · warehouse · modelling · files · catalogues · table · snapshots · governance · boundaries · selecting · design · operational workload · analytical workload · materialized view · fact table · dimension · slowly changing dimension · catalogue · manifest · orphan file · table snapshot · atomic metadata publication · field id · data lineage · metric owner · data minimization · workload specification · freshness objective · architecture trade-off17 min
- 43Columnar Storage and CompressionA report often needs a few fields from many records. Columnar storage arranges values so the engine can avoid reading unrelated fields and can exploit…rows · versus · columns · encodings · compression · blocks · predicate · pushdown · statistics · skipping · memory · input-output · trade-offs · columnar storage · row group · projection pruning · dictionary encoding · run-length encoding · delta encoding · lossless compression · compression block · read amplification · predicate pushdown · candidate row · zone map · conservative pruning · data clustering · vectorized execution · decode cost · end-to-end measurement17 min
- 44Full-Text Search and RelevanceLooking up an exact order ID and finding a useful document are different tasks. Text search must decide how to split language, which expressions match…words · documents · tokenisation · inverted · indexes · scoring · ranking · language · spelling · evaluating · search · quality · document · information need · candidate retrieval · lexeme · analyzer · inverted index · posting list · positional index · document frequency · bm25 · tie-break · query expansion · edit distance · snippet · precision · recall · reciprocal rank16 min
- 45Vector Search: Similarity Is Not TruthVector search represents items as lists of numbers and retrieves items that are close under a chosen mathematical rule. It can find useful similarities…representing · items · vectors · distance · similarity · exact · approximate · search · index · trade-offs · filtering · evaluation · retrieval · limits · embedding · embedding space · representation compatibility · euclidean distance · inner product · cosine similarity · nearest neighbour · approximate nearest-neighbour search · candidate recall · hnsw · ivf index · product quantization · eligible set · post-filtering · overfetching · hybrid retrieval · grounded answer · retrieval boundary17 min
- 46Metrics, Bias and Honest AnalysisA metric is a precisely defined question expressed as a number. The calculation can be flawless while the definition, population or interpretation is…metric · definition · denominators · populations · missingness · selection · effects · association · versus · cause · communicating · uncertainty · metric definition · operationalization · restated series · denominator · case mix · standardization · observed-only statistic · sensitivity bound · selection bias · sampling frame · information leakage · confounder · estimand · confidence interval · wilson interval · statistical unit16 min
- 47Permissions, Secrets and Tenant BoundariesFinding a record and being allowed to read it are different questions. A correct query can return information to the wrong person. This chapter adds an…least · privilege · database · application · checks · tenant · separation · secret · handling · adversarial · boundary · tests · principal · authorisation · revocation delay · least privilege · effective privilege · runtime identity · row-level security · connection context · policy bypass · scoped key · confused deputy · rotation · revocation · negative control · policy oracle · boundary coverage19 min
- 48Retention, Deletion and Data LineageInformation has a useful lifetime. Keeping it forever can create unnecessary exposure; deleting it carelessly can destroy evidence, break references or…purpose · record · classes · retention · policies · deletion · across · copies · derived · data · lineage · backups · exceptions · evidence · record class · purpose limitation · data minimisation · retention trigger · hold · policy version · logical deletion · sanitisation · store inventory · incremental maintenance · recomputation · reintroduction · restricted retention · cryptographic erasure · completion predicate · verification scope · residual copy18 min
- 49Schema Changes Without SurprisesA schema change alters the agreement between stored records and the programs using them. The challenge is not merely to make a new table definition…compatibility · windows · expand · contract · backfills · validation · cutover · rollback · versus · roll-forward · staged · evidence · compatibility window · consumer · semantic compatibility · authoritative representation · backfill · keyset progress · transformation precondition · reconciliation · validation boundary · irreversible transformation · precondition · artefact identity · rehearsal17 min
- 50Observability, Capacity and CostA running system produces signals about its behaviour. Useful observability connects those signals to questions: Are users completing their work? Where…signals · tied · user · outcomes · logs · metrics · traces · storage · growth · saturation · headroom · cost · attribution · operational · service-level indicator · service-level objective · error budget · log · metric · trace · cardinality · logical payload · net growth · intervention threshold · admission control · retry amplification · allocated cost · marginal cost · cost boundary · runbook · forecast error · operational owner17 min
- 51Capstone: From One Shop to a Multi-Branch ServiceWe began with a person recording a sale. We can now name the contracts, representations, queries, transactions, copies and operational responsibilities…requirements · boundaries · schema · workflows · correctness · under · retries · reporting · reconciliation · recovery · access · tests · review · release · accepted operation · scope boundary · exclusion · row grain · agreed price snapshot · transaction ownership · idempotency scope · outbox · inbox · acknowledgement loss · reconciliation population · effect count · external outcome · fault injection · restore rehearsal · integrity check · executable assertion · release manifest · evidence boundary19 min
- 52The Reference Desk: Glossary and Diagnostic GuidesThis chapter is a place to return when a term, query or failure needs a precise next step. It is not a substitute for the explanations earlier in the…plain-to-technical · glossary · data-type · reference · diagnostic · decision · guides · design-review · questions · test · recovery · templates · source · version · cross-reference · implementation boundary · query grain · tie-breaker · representation contract · symptom · hypothesis · bounded observation · safety property · progress property · fault model · test fixture · reproducibility record · skipped check · primary source · consultation date · version register19 min