BackpressureConcept

A queue that cannot say no is a queue that will fall over.

CAP, In PracticeConcept

You do not choose between C and A; you choose what to do during a partition.

CRDTsConcept

Data types whose merge function is associative, commutative and idempotent — so replicas converge without coordination.

Consistent HashingConcept

Adding a node should move 1/n of the keys, not all of them.

Exponential Backoff with JitterConcept

Retries without jitter re-synchronise your clients into a self-inflicted DDoS.

Idempotency KeysConcept

The client picks a unique key so a retried request runs at most once.

RaftConcept

Consensus you can actually hold in your head: one leader, an append-only log, a majority.

Read-Your-Writes ConsistencyConcept

The weakest guarantee that stops a user seeing their own edit vanish.

Vector Clocks and Logical TimeConcept

Wall clocks cannot order events across machines; counters can.

Connection Pooling and Pool ExhaustionConcept

A Postgres connection is a process; the pool is the real concurrency limit.

Index SelectivityConcept

An index helps only when it eliminates most of the table.

LSM TreesConcept

Trade read amplification for write throughput by never updating in place.

MVCCConcept

Readers never block writers because each sees its own snapshot of history.

Write SkewConcept

Two transactions that are individually correct can break an invariant together.

Circuit BreakerConcept

Stop calling a dependency that is already failing, so you fail fast instead of piling up.

Saga PatternConcept

No distributed transaction: a sequence of local commits, each with a compensating undo.

Transactional OutboxConcept

The only reliable way to both commit a row and publish an event.

False SharingConcept

Two threads touching different variables on the same cache line fight over it.

Thundering Herd and Cache StampedeConcept

One expired key, a thousand simultaneous recomputations.

Bloom FiltersData structure

A few kilobytes that tell you, with no false negatives, what is definitely absent.

Structured ConcurrencyConcept

A task cannot outlive the scope that started it.