Posts (238+)

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September 2026

Leaky Bucket:Smooth Bursts Into a Steady Drain

Queue work into a bucket that leaks at a constant rate — overflow is dropped or the caller waits. Smooth output, not a stored burst of tokens.

Design Patterns

Bridge:Split Abstraction from Implementation

Stop the Email×SendGrid / SMS×Twilio subclass grid by letting OrderNotifier hold a MessageSender so channels and vendors vary independently.

Algorithms

KMP:Find a Pattern Without Sliding Back on the Text

Build the LPS prefix table, then scan the text once — on a mismatch the pattern jumps using already-matched prefix, so the text index never retreats.

Design Patterns

Iterator:Walk a Collection Without Exposing Its Guts

Stop walking Order line items with get(i) on a leaked ArrayList so a switch from list to a SKU tree does not rewrite OrderProcessor.

Algorithms

Token Bucket:Allow Bursts, Then Enforce an Average Rate

Refill tokens at a steady rate, spend one per request, and allow a burst up to bucket capacity — then reject or wait.

Design Patterns

Abstract Factory:Families of Objects Without Naming the Concrete Types

Build Stripe-region and Razorpay-region checkout families in Java so gateway, webhook parser, and money type vary together without OrderProcessor naming the concretes.

Algorithms

Prim:Grow an MST From a Seed Vertex

Grow a min-heap of crossing edges from a seed until every vertex is in the tree — a Dijkstra-shaped frontier for an MST, not distances from a source.

Design Patterns

Chain of Responsibility:Pass a Request Until Someone Handles It

Replace a hard-coded fraud-inventory-payment-notify sequence with a Handler chain in Java so a new checkout step is a class you splice in, not a next-type you edit.

Algorithms

Consistent Hashing:Move Few Keys When a Node Joins or Dies

Place keys on a ring so adding or removing a node remaps only its neighbors — not every key — with virtual nodes to even the load.

Design Patterns

State:Change Behavior When Internal State Changes

Replace a growing DRAFT / PAID / REFUNDED / VOID switch in process, refund, and void with OrderStatus objects that own legal transitions, so OrderProcessor stops being the state machine.