Database terms
Where your data lives, breathes, and occasionally panics
Almost every application is, at its core, a system for reading and writing data. This category covers relational and non-relational databases, query optimisation, indexing strategies, transactions, normalisation, replication, and the CAP theorem trade-offs that dictate how distributed data behaves. Choosing and using the right database correctly is one of the highest-leverage skills in backend development.
Optimistic Locking
A concurrency pattern using a version column to detect conflicting concurrent writes — no row locks held between read and write.
1mo ago
database advanced
SELECT FOR UPDATE
A locking read that acquires exclusive row locks — preventing other transactions from modifying selected rows until commit.
1mo ago
database advanced
Change Data Capture (CDC)
A pattern for tracking and streaming every insert, update, and delete from a database — by reading the database's internal transaction log rather than polling tables — enabling real-time event-driven integrations without impacting query performance.
2mo ago
database advanced
Write-Ahead Log (WAL)
A durability technique where changes are written to an append-only log before being applied to the database — if the system crashes, the log is replayed to restore the database to a consistent state.
2mo ago
database advanced
Column-Level Encryption PHP 7.1+
Encrypting sensitive database columns (SSN, credit card, medical data) — application holds the key; database never sees plaintext; breach exposes only ciphertext.
2mo ago
database advanced
Eventual Consistency in Databases A consistency model where replicas are not immediately synchronised — all nodes will converge to the same state given no new writes, trading consistency for availability and partition tolerance.
2mo ago
database advanced
Graph Databases
Databases where relationships are first-class citizens — Neo4j, Amazon Neptune — optimised for traversing complex networks of connected entities that are expensive in relational databases.
2mo ago
database advanced
PostgreSQL VACUUM & ANALYZE PHP 5.0+ VACUUM reclaims storage from dead tuples created by MVCC updates and deletes. ANALYZE updates query planner statistics. Both are essential for PostgreSQL performance.
2mo ago
database advanced
Composite Index Design PHP 5.0+ A composite index covers multiple columns — column order determines which queries benefit, following the leftmost prefix rule.
2mo ago
database advanced
Database Deadlocks PHP 5.0+ A situation where two or more transactions hold locks the other needs, each waiting indefinitely — resolved by the database killing one transaction.
2mo ago
database advanced
EXPLAIN ANALYZE PHP 5.0+ The database command that shows the actual execution plan of a query — revealing sequential scans, missing indexes, and row estimate errors that cause slow performance.
2mo ago
database advanced
Pessimistic vs Optimistic Locking PHP 5.0+ Pessimistic locking acquires a database lock upfront preventing conflicts. Optimistic locking detects conflicts at write time using a version column — trading lock overhead for conflict detection.
2mo ago
database advanced
SQL Window Functions PHP 5.0+
SQL functions that perform calculations across a set of rows related to the current row without collapsing them into a single output row.
2mo ago
database advanced
Transaction Isolation Levels PHP 5.1+ SQL standards defining how and when changes made by one transaction are visible to others, trading consistency for concurrency.
2mo ago
database advanced