notes

Distributed Systems

• Idempotency Keys and Retry Semantics How to make mutation retries safe by binding idempotency keys to parameters, results, and dedupe windows.
• Leader Election and Lease Safety Consensus election invariants, lease timing risks, stale leaders, and fencing tokens for side-effect safety.

Reliability

• Async Backpressure and Bounded Queues How bounded queues, overload policy, cancellation, and admission control keep async services from failing slowly.

Rust Services

• Rust Error Boundaries in Services How to separate recoverable errors, bugs, transport responses, retryability, and logging context in Rust services.

Verification

• Property Tests for Parsers and Protocols How property-based tests expose parser and protocol bugs through invariants, generators, shrinking, and round trips.

Operations

• Observability for Debuggable Systems How logs, metrics, traces, correlation IDs, and cardinality limits make production failures explainable.

Networking

• GRE, FOU, and NAT Traversal Design notes for carrying GRE through UDP, coordinating peers, and validating tunnel behavior on Linux.
• Linux Network Namespaces and Packet Paths A practical model for namespaces, veth pairs, bridges, routing, NAT, and where packets disappear.

Internals

• Epoll Readiness and Nonblocking IO How readiness notification, nonblocking file descriptors, draining loops, and backpressure fit together.

Performance

• io_uring Fixed Buffers and Parser Fuzzing Notes on reducing allocation and copy overhead while keeping protocol parsers testable under fuzzing.

Foundations

• Backpropagation as Credit Assignment How gradients move credit through a computation graph, where they fail, and what to check when training is unstable.
• Loss Functions and Optimization Behavior What common losses reward, how gradients behave, and why metric alignment matters more than loss names.

Training

• Batching, Gradient Accumulation, and Throughput How batch size, accumulation, optimizer steps, and hardware utilization interact during training.
• Mixed Precision Training and Numerical Stability Practical rules for fp16, bf16, loss scaling, overflow, underflow, and stable training loops.

Evaluation

• Model Evaluation Beyond Accuracy Metric selection, confusion-matrix rates, calibration, uncertainty, and why accuracy is often the wrong launch gate.
• Train, Validation, and Test Leakage How leakage creates fake model quality through split mistakes, preprocessing, duplicates, and time travel.

Inference

• Inference Latency, Batching, and KV Cache Serving tradeoffs for throughput, tail latency, autoregressive decoding, batching, and key-value cache memory.

Retrieval

• Vector Search and Embedding Retrieval Embedding search basics, distance metrics, approximate indexes, recall tradeoffs, and retrieval evaluation.

Board Design

• RF PCB Layout and Signal Integrity Practical control of stackup, return fields, transitions, and test structures on RF and mixed-signal boards.

Measurement

• RF Measurement and VNA Workflow A repeatable workflow for defining reference planes, calibrating a VNA, and preserving credible RF evidence.

Board Design

• PCB Design and Bring-Up A review and first-power workflow centered on current paths, test access, and recoverable failures.

Measurement

• Measurement and Instrumentation Probe loading, bandwidth, aliasing, uncertainty, and evidence practices for measurements that survive review.

EMC and Grounding

• EMC, EMI, and Grounding A source-path-victim workflow for controlling conducted, common-mode, and radiated interference.

STM32

• STM32 Bare-Metal Bring-Up A staged STM32 bring-up flow from clocks and reset through one observable peripheral at a time.

Concurrency

• Interrupts, DMA, and Ring Buffers Practical rules for moving bytes between ISRs, DMA, and foreground code without blocking or corrupting shared state.

Control Loops

• PID Tuning and Step Response A practical PID workflow based on measured step response, saturation behavior, and repeatable tuning records.

State Estimation

• IMU Calibration and Drift How to characterize accelerometer and gyro errors before trusting dead reckoning or attitude estimates.

Underwater Systems

• UUV Navigation and State Estimation Sensor roles, estimator integrity, calibration, and error-budget discipline for navigation without continuous GNSS.
• UUV Underwater Communications and Networking Protocol and test design for heterogeneous UUV networks with scarce, delayed, and intermittent acoustic links.

Verification

• Design Verification and Test A requirement-to-evidence workflow for credible qualification, acceptance, failure handling, and test records.