Search

Lessons (40)

• Transactions, Indexes & Concurrency

  … Atomicity is all-or-nothing; consistency preserves constraints; isolation defines concurrent visibility; durability survives failure. Never wait for …

• React Internals & Concurrent Rendering

  Understand reconciliation, render versus commit, batching, Suspense and concurrent rendering so React performance fixes target the work users …

• Concurrency, Resilience & Distributed Workflows

  … Timeouts and bounded concurrency are just as important as retries. Workers, scheduling and backpressure Use background workers for …

• Go Concurrency: Goroutines, Channels and Context

  Concurrency vs parallelism, goroutines and the scheduler, buffered and unbuffered channels, select, WaitGroup, Mutex and atomics, worker pools …

• 10,000 Users Do Not Need 10,000 Database Connections

  … When that query finishes, the connection returns to the pool and another request can borrow it. HTTP concurrency …

• Rust: Types, Errors and Concurrency

  … That's the compiler catching a race before it exists. Async with Tokio For thousands of concurrent network …

• Backend Languages: Node.js, Go, Python & Rust

  … How each handles concurrency, what it's best at, and the same tiny API written in all four …

• Serverless: Lambda and API Gateway

  … Reserved concurrency can bound a function's concurrency; throttling still needs a client and retry strategy. A new …

• Event-Driven Patterns, Step Functions and Reliable Lambdas

  … A conditional claim prevents concurrent workers from starting the same operation, but external side effects also need idempotency …

• Debug Latency Like an Investigator

  … Correlate the release with changed query shape or concurrency. 3. Mitigate with rollback or reduced concurrency, then fix …

• Timeouts, Retries & Backpressure

  … Cap shipping concurrency and queue length independently of other dependencies. Reject excess work or return a clear pending …

• Resilient Service Calls: Retries, Breakers and Load Shedding

  … Jitter, limited half-open probes and bounded concurrency prevent a synchronized recovery surge. A breaker without admission control …

• Choosing a Programming Language

  … How to compare JavaScript/TypeScript, Python, Go and Rust by runtime, typing, concurrency and team fit, plus the …

• Collaborative Document Editing & Real-Time Sync

  … converge concurrent and offline edits with a fenced per-document sequencer, a durable op log, CRDT merge and …

• ACID, Transactions & Locks

  … changes or rolls back; locks and isolation protect concurrent writers](/img/database/acid.svg) ACID without vague definitions …

• Design a Polite Web Crawler

  … global concurrency of 1,000 is still rude if all 1,000 hit one small website. Respecting robots …

• Capacity, Availability, Latency and CAP

  … Estimate bytes, concurrency and growth separately. 2. Define latency and availability targets for specific endpoints. An aggregate average …

• StatefulSets, DaemonSets, Jobs and CronJobs

  … schedule: "0 2 " concurrencyPolicy: Forbid skip if the last run is still going successfulJobsHistoryLimit: 3 failedJobsHistoryLimit: 3 jobTemplate …

• Serverless Architecture

  … it scales and bills mermaid xychart-beta title "Concurrent function instances follow traffic" x-axis ["00:00", "06 …

• Flash Sale: 10 Million Buyers, No Oversell

  … sold out. Never separately “check available” then decrement: concurrent requests race. Give every purchase an idempotency key, reconcile …

• Database Indexing & Transactions

  … Learn how B-tree indexes work, how to read a query plan, and how isolation levels prevent concurrency …

• DBMS Foundations, Keys & Normalization

  … Why DBMS instead of files? A DBMS centralizes data, supports concurrent access, transactions, constraints, authorization, backup/recovery and …

• A WhatsApp OTP Is Only Single Use If You Make It So

  … Under the default READ COMMITTED isolation, a second concurrent UPDATE waits for the first to commit, then re …

• Indexes, EXPLAIN & Query Plans

  … Remove unused indexes carefully, and create large production indexes with the engine-safe online/concurrent method where available.

• Resilience Patterns

  … give each dependency its own limited pool of connections, threads or concurrent calls. A slow recommendations service can …

• Async JavaScript: Promises, async/await and Node's Event Loop

  … pending → fulfilled or rejected, once. - await independent work together with Promise.all ; limit concurrency for large batches. - Every …

• Code Profiling

  … sorting, serialization, hot loop Throughput drops Queue depth, concurrency, wait time and saturation Slow dependency, lock contention, exhausted …

• Time, Consistency and Distributed Transactions

  … Lamport clocks establish a causal ordering; vector clocks can identify concurrent updates. Network partitions can create split brain …

• Dependencies, Data Sources, and Resource Lifecycle

  … Independent resources can run concurrently. Use depends on only for a dependency that is not represented by a …

• Real-Time, Pub/Sub, Webhooks and CDC

  … Track webhook attempts durably, sign requests, bound retry age and concurrency, and deduplicate at consumers. CDC can capture …

• AWS Databases: Choose the Right One

  … A larger database does not fix incorrect concurrency logic. Connections are a finite resource If 20 app copies …

• The Hot SKU Alert Problem

  … They are questions about ownership, ordering, concurrency, delivery semantics and failure recovery. Separate the price write from the …

• Caching, Consistent Hashing and Sharding

  … Cache product reads with a defined freshness bound and coalesce concurrent cache misses. 2. Use consistent hashing to …

• CI/CD and Reviewed Production Changes

  … Two jobs writing the same state should not race; use both backend locking and CI concurrency controls. Commands …

• Multi-Region and Disaster Recovery

  … Active-active means multiple regions write concurrently; it needs conflict resolution, request routing and careful ownership. Do not …

• L6 Production Debugging Casebook

  … An index may help find the beginning, but it does not make skipped rows free; concurrent inserts can …

• Design a URL Shortener

  … Limit fallback concurrency and coalesce misses instead of sending all 10,000 requests/s to storage. A disabled …

• Payment Retries: Prevent Duplicate Charges

  … try again” Retry means “look up this attempt” Concurrent requests race A unique key permits one attempt State …

• The L6 System-Design Thinking Loop

  … seat twice. How to prove it worked Run concurrent last-seat requests and inject a crash after provider …

• Production Capstone and Interview Practice

  … accompanying plan can still propose modifications. What prevents concurrent applies? Backend locking and a serialized delivery path. Locks …