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A disk hides mechanical seek and rotation behind a linear block API; modern I/O then uses memory-mapped registers, DMA queues, and interrupts so the CPU mainly issues commands and receives completions.
A file system maps durable byte collections onto disk blocks; contiguous, linked, and FAT allocation trade locality, growth, random access, and metadata cost.
The 4.3BSD inode uses direct, single-indirect, and double-indirect tiers so lookup depth scales with file size; FIFO, SPTF, SCAN, and CSCAN then trade seek cost, fairness, and wait time.
Block cache retains hot indexes, bitmap slack preserves placement choices, and fragments plus delayed allocation trade later, better information for locality.
Directories map text names to file-system-local inode numbers; hard links share inode identity and reference counts, while symlinks store paths and permit cross-filesystem references with loops and dangling targets.
A single file-system operation updates several blocks, but a crash can occur between any two writes; this lecture compares how fsck, ordered writes, and write-ahead logging trade recovery time, performance, durability, and consistency.
Lecture 24 continues from the WAL entry point into transactions, idempotent replay, and checkpoints, showing why consistency is not durability and why a journal does not replace fsync or backups.
Lecture 25 separates assumption, inference, and substitution as ways to establish trust, then examines how social recommendations, generative AI, and synthetic media amplify over-trust; the response is preserved provenance, independent validation, and coordinated responsibility.
Flash programs pages but erases whole units; an FTL hides the asymmetry with out-of-place mapping, then manages amplification through garbage collection, temperature segregation, wear leveling, and TRIM.
A VM expands the process interface into a machine interface; the hypervisor directly executes ordinary instructions, traps privileged operations, and virtualizes interrupts, I/O, and two-stage address translation.
Lecture 28 reduces the semester to concurrency, memory, and storage, then uses four ideas—virtualization, atomicity, locality, and layering—to explain how operating systems manage shared resources.
Ably manages global realtime connections, channels, presence, and short-window recovery; applications still own idempotency, durable business state, token capabilities, and offline resynchronization.
An agent should execute one task with a short-lived, audience- and permission-restricted credential while preserving user and agent identities, execution-time authorization, confirmation, and audit lineage.
Agent execution must constrain kernels, filesystems, processes, networks, credentials, and tool authorization; sandbox escape is only one path, and an overpowered API token is often more direct.
Linode is now the compute foundation of Akamai Cloud Computing; VMs, LKE, storage, and databases retain regional and network boundaries, so the Akamai brand does not imply complete integration.
Algolia packages indexing, search-as-you-type, facets, and UI components as a hosted service; it ships quickly, but data synchronization, relevance, and usage costs remain your responsibility.
Kafka is a distributed log ordered by partition and retained by policy. Consumer groups divide work through offsets, while exactly-once processing holds only inside boundaries covered by Kafka transactions.
Pulsar separates serving from storage: stateless brokers handle connections while BookKeeper stores ledgers and subscription cursors. Elasticity and multi-tenancy come with more operational components.
Appwrite combines Auth, TablesDB, Storage, Functions, Realtime, and Messaging behind consistent APIs; Cloud and self-hosted products resemble each other but have different operational ownership.
assistant-ui separates Agent Chat into headless React primitives, a conversation runtime, and backend adapters, so the UI does not have to bind directly to one model SDK's message state.