Databases & Storage
12 clusters, spanning half-life layers 0–3: Relational, Managed & serverless SQL, Document stores, Key-value & caching, Wide-column, Graph, Search engines, Vector databases, Time-series, Distributed SQL, ORMs & query builders, Core concepts.
Clusters
Section titled “Clusters”Relational
The relational model, transactions, the query planner and index strategy transfer across every engine and are almost the whole subject. Procedural…
Managed & serverless SQL
Whatever engine sits underneath transfers completely. What is new is the operational envelope — connection limits, cold starts, branching, and which…
Document stores
Denormalised modelling, embed-vs-reference and query-shaped documents transfer across all of them and are the actual skill. Aggregation syntax and…
Key-value & caching
Eviction policy, TTL discipline, cache-aside vs write-through and the invalidation problem transfer everywhere, including to CDNs. DynamoDB is in…
Wide-column
Partition key design decides everything, and that lesson transfers across all four and into DynamoDB. Consistency tuning and repair operations are…
Graph
Thinking in traversals rather than joins is the transferable shift. Query languages split hard — Cypher and Gremlin share no syntax and barely share…
Search engines
Inverted indexes, analysers, tokenisation and relevance scoring transfer across every member and are Layer 1 knowledge. Query DSLs and cluster…
Vector databases
Embedding dimensionality, distance metrics, ANN index types and the recall/latency trade transfer across all of them and are the whole content. APIs…
Time-series
Downsampling, retention policies, continuous aggregates and the write-heavy/append-only access pattern transfer across all three.
Distributed SQL
SQL surface transfers from the relational cluster almost completely. What is new — and what bites — is that latency is now a function of data…
ORMs & query builders
The N+1 problem, lazy vs eager loading, the identity map and the migration lifecycle transfer across every ORM in every language. Fluent APIs and…
Core concepts
Layer 0 and the reason to spend real time in this domain: isolation levels, index structures and replication trade-offs outlive every product on this…