N+1 Problem & Fetching

N+1 means 1 query loads N parents, then N separate queries load each parent's lazy collection – fix with JOIN FETCH (one query), @EntityGraph (declarative), or @BatchSize (batched lazy loads).

LAZY loads related entities only when accessed (via proxy); EAGER loads them immediately with the parent – always override @ManyToOne to LAZY and fetch what you need inside the transaction.