Shipment Tracking Service: Low Level Design Core Data Model The tracking service maintains two primary tables: Shipment (one record per […]

Ephemeral State Design Typing state is intentionally ephemeral — stored only in Redis, never persisted to the database. There is

Presence States online — active heartbeat within the last 30 seconds away — active within the last 5 minutes but

Graph-Based Recommendation Engine Model the recommendation problem as a graph: users and items are nodes, interactions are weighted edges. Graph

What Is a Rule Engine? A configurable rule engine evaluates business logic defined as structured data rather than code. Rules

What Is an Anomaly Detection Service? An anomaly detection service monitors time-series metrics and identifies values that deviate significantly from

WebAuthn / FIDO2 Overview Passkeys use public-key cryptography. The private key never leaves the device; the server stores only the

Schema Reaction ( entity_type VARCHAR(50), entity_id BIGINT, user_id BIGINT, reaction_type ENUM(‘like’,’love’,’haha’,’wow’,’sad’,’angry’), created_at TIMESTAMP, PRIMARY KEY (entity_type, entity_id, user_id) ) ReactionCount

Data Model Closure table for efficient subtree queries: ThreadAncestor ( ancestor_id BIGINT, descendant_id BIGINT, depth INT, PRIMARY KEY (ancestor_id, descendant_id)

PoP Selection and GeoDNS When a client issues a DNS query, GeoDNS maps the client IP to a geographic region

ETA Calculator Service: Low Level Design Road Network Graph Schema Node (Intersection) ——————- id BIGINT PK lat DOUBLE PRECISION lng

Location Sharing Service: Low Level Design Data Model Location Table (Time-Series) Location ——– device_id BIGINT lat DOUBLE PRECISION lng DOUBLE

Geo-Fencing Service: Low Level Design Data Model GeoFence Table GeoFence ——– id BIGINT PK name VARCHAR(255) type ENUM(‘circle’,’polygon’) center_lat DOUBLE

Overview An SSH key rotation service automates generation of new keypairs, distribution to all target hosts, a grace period with

Overview A secrets manager provides secure storage, access control, and lifecycle management for credentials, API keys, and other sensitive values.