Step 12: Technical Glossary

Simple, precise definitions of technical terms used across OmniPost (20-notification-delivery-platform).

• AsyncIO: Python's built-in asynchronous framework using an event loop to achieve cooperative multitasking without OS thread overhead.
• Circuit Breaker: A resilience design pattern that detects upstream provider failures and temporarily diverts traffic to prevent cascading system crashes.
• Dead-Letter Queue (DLQ): A storage buffer that holds messages that have repeatedly failed delivery and exhausted all retry attempts, isolating them for manual inspection.
• Exponential Backoff: An algorithm that exponentially increases the wait time between retry attempts (e.g. 1s, 2s, 4s, 8s) to give recovering services time to stabilize.
• Full Jitter: A randomization technique added to exponential backoff that uniformly spreads retry delays between zero and the calculated ceiling to prevent thundering herd spikes.
• HMAC-SHA256: Hash-based Message Authentication Code combining a cryptographic hash function with a secret key to verify data integrity and authenticity.
• Idempotency Key: A unique client-supplied token that guarantees performing the same operation multiple times produces the exact same outcome without duplicate actions.
• Jinja2 SandboxedEnvironment: A restricted AST execution environment that disables access to Python internal methods and dangerous built-ins to block Server-Side Template Injection.
• Lease-Based Locking: A distributed concurrency pattern where a worker claims a job for a limited duration (locked_until); if the worker dies, the lease expires and another worker reclaims it.
• Monotonic State Machine: A finite state machine whose status transitions can only move forward along allowable paths, never regressing to previous states.
• Provider Capability Matrix: A registry defining the features, maximum payload sizes, channels, and costs supported by each third-party delivery vendor.
• Quiet Hours: Defined nighttime hours (e.g. 22:00 to 08:00) during which non-critical promotional notifications are suppressed to respect user privacy and telecom regulations.
• Role-Based Access Control (RBAC): An authorization approach where permissions are assigned to roles (ADMIN, OPERATOR, VIEWER), and users are assigned to roles.
• Starvation Protection: An algorithm that promotes aged, low-priority tasks when high-priority tasks continuously monopolize worker processing capacity.
• Token Bucket Rate Limiter: An algorithm that maintains a bucket of tokens refilled at a constant rate; each request consumes a token, allowing controlled bursts while enforcing average throughput.