Blog

Practical engineering articles: debugging deep dives, framework guides, and patterns you can apply at work and in interviews.

AI Mock Interview Platform: System Design at Scale

Design an AI mock interview platform for one million candidates: real-time voice loop, GPU model serving, stateful sessions, scoring, failover, and cost.

August 23, 2026

Context Engineering Interview Guide: Prompts, Memory, Retrieval, Compression, and Context Windows

Context engineering explained for interviews: how to assemble prompts, memory, retrieval, and compression into a token budget the context window can actually hold.

August 22, 2026

AI Agent Security Interview Guide

Prepare an AI agent security interview answer covering prompt injection, excessive agency, tool abuse, identity, approvals, sandboxing, testing, and response.

August 20, 2026

How to Evaluate AI Agents: Task Success, Tool Accuracy, Regression Tests, and Human Review

A production guide to evaluating AI agents with end-state task success, tool-call accuracy, regression suites, human review, and release gates.

August 20, 2026

LLM Observability System Design with OpenTelemetry

Design production LLM observability with OpenTelemetry: trace tokens, latency, cost, tool calls, sampling, privacy, evaluation, and reliable alerts at scale.

August 20, 2026

Design a Production RAG System in 2026

Design a production RAG system with hybrid search, reranking, evaluation, caching, security, capacity planning, and deployment tradeoffs for interviews.

August 3, 2026

How to Design a Multi-Agent System: Orchestration, Memory, Tool Calling, and Failure Recovery

A production guide to multi-agent orchestration, scoped memory, safe tool calling, durable checkpoints, recovery, evaluation, and interview trade-offs.

August 3, 2026

MCP System Design: Secure Multi-Tenant Gateway

Design a secure multi-tenant MCP gateway in TypeScript with tenant isolation, OAuth, policy enforcement, routing, scaling, testing, and interview tradeoffs.

August 3, 2026

MCP vs A2A vs A2UI: A System Design Guide for AI Agent Architectures

Choose MCP, A2A, or A2UI by architecture boundary, with a protocol decision tree, TypeScript example, failure modes, and interview trade-offs.

August 3, 2026

AI Coding Interviews in 2026: What Senior Engineers Should Prepare For

Prepare for AI-assisted coding interviews in 2026: architecture judgment, agent supervision, debugging, verification, tests, and senior-level communication.

August 2, 2026

Fix RuntimeError: CUDA out of memory (PyTorch)

Fix PyTorch CUDA out-of-memory errors with profiling, batch and sequence controls, AMP, checkpointing, allocator tuning, distributed fixes, and GPU diagnostics.

July 31, 2026

Fix Hydration Failed Errors in Next.js

Fix Next.js hydration mismatch errors by matching server and first client output, debugging dates, storage, invalid HTML, CSS, CDN, and production-only changes.

July 28, 2026

Fix EADDRINUSE: Address Already in Use in Node.js

Fix Node.js EADDRINUSE on port 3000: find the listener safely, resolve duplicate servers, and prevent Docker, WSL, CI, and production port clashes reliably.

July 27, 2026

Fix npm ERESOLVE Dependency Tree Errors

Fix npm ERR! ERESOLVE dependency tree errors by reading peer conflicts, aligning package versions, using overrides safely, and keeping CI installs reproducible.

July 27, 2026

Fix TypeError: datetime Is Not JSON Serializable

Fix Python datetime JSON serialization errors with ISO 8601, timezone-safe encoders, Flask, Django, FastAPI, pandas, debugging, tests, and prevention.

July 27, 2026

Fix AttributeError: 'DataFrame' object has no attribute 'append'

Pandas 2.0 removed DataFrame.append(). Replace it with pd.concat — and if you were appending in a loop, collect rows in a list and build the DataFrame once.

July 25, 2026

Fix ImportError: cannot import name 'Mapping' from 'collections'

Python 3.10 removed the old collections.Mapping alias. Import from collections.abc instead — but it's usually an old dependency, so read the traceback and upgrade it.

July 25, 2026

Fix ModuleNotFoundError: No module named 'cv2' (OpenCV)

You import cv2 but the pip package is opencv-python — and there are four variants. Pick the right one, and preempt the libGL.so.1 error on servers with headless.

July 25, 2026

Fix ModuleNotFoundError: No module named 'dotenv'

The package is python-dotenv but the import is dotenv — and pip install dotenv is the wrong package. Install python-dotenv into the interpreter you actually run.

July 25, 2026

Fix ValueError: too many values to unpack (expected 2)

This means the left side has fewer targets than the right side has values. Count both sides, iterate dicts with .items(), and use star-unpacking for extras.

July 25, 2026

Fix OpenAI RateLimitError (429): The Complete Guide

OpenAI RateLimitError has two causes that need opposite fixes: insufficient_quota (billing) and rate_limit_exceeded (throughput). Diagnose which, then fix it.

July 24, 2026

Fix "Token indices sequence length is longer than the specified maximum"

This Hugging Face message is a warning, not the real error — the crash comes later. Fix it with explicit truncation, and watch for the model_max_length sentinel trap.

July 24, 2026

Fix "bitsandbytes CUDA Setup failed"

If bitsandbytes loads libbitsandbytes_cpu.so, no CUDA binary matched. Upgrade bitsandbytes first, confirm a CUDA PyTorch, then fix the library path.

July 24, 2026

Resolve "ChromaDB collection does not exist"

Two causes account for almost every ChromaDB 'collection does not exist' — using get_collection instead of get_or_create, and an ephemeral client that never persisted.

July 24, 2026

Resolve "CUDA error: device-side assert triggered"

The traceback lies because CUDA runs async. Get the real line with CUDA_LAUNCH_BLOCKING=1 or the CPU, then fix the out-of-range index behind it.

July 24, 2026

Resolve "Hugging Face 401 Unauthorized"

A Hugging Face 401 means the token is missing, invalid, or lacks access. Learn to tell 401 from 403 and 404, and fix gated and private repo access.

July 24, 2026

Resolve "LangChain ValidationError"

A LangChain ValidationError is a Pydantic error — and it names the exact field. Read loc/type/input, and fix the Pydantic v1 vs v2 mismatch behind most of them.

July 24, 2026

Resolve "OSError: Can't load tokenizer"

This Hugging Face error means one of two things: a Hub id that can't be found, or a local folder missing tokenizer files. Learn which, then fix it fast.

July 24, 2026

Fix "SentenceTransformer model download failed"

"Download failed" isn't one error. Triage it by symptom — wrong name, gated auth, network/SSL/proxy, timeout, or a corrupted cache — and apply the right fix.

July 24, 2026

Fix torch.cuda.is_available() Returns False

The fastest test is torch.version.cuda — if it's None you have a CPU-only wheel. PyTorch bundles its own CUDA runtime, so you only need the NVIDIA driver.

July 24, 2026

Angular Unit Testing with Jasmine and Karma: A Practical Guide

How Angular unit testing fits together — TestBed, Jasmine, and Karma — plus code coverage, testing pipes, and testing attribute directives, with examples.

July 21, 2026

Fix CUDA and cuDNN Library Load Errors in TensorFlow: A Diagnostic Guide

Every TensorFlow CUDA library error — libcublas, libcudart, libnvinfer, cuDNN — traced to one of four root causes, with the order to diagnose them.

July 21, 2026

JavaScript Algorithm Interview Problems: 8 Patterns with Solutions

Learn eight JavaScript algorithm interview patterns with worked solutions: array transforms, hashing, interval scans, matrix rotation, and async sequencing.

July 21, 2026

Common Pandas Errors and Gotchas: A Diagnostic Guide

The pandas errors that waste the most time — SettingWithCopyWarning, Int64Index errors, silent assignment failures, and merge row explosions — and their causes.

July 21, 2026

Honesty and Psychological Safety in Engineering Teams

Why engineers overstate confidence in their code — deadline pressure, fear, and review cultures that punish doubt — and the practices that fix it.

May 26, 2026

Google AI Edge Gallery: Running AI Models Directly on Your Phone

Google AI Edge Gallery runs generative AI models fully on-device on Android — no cloud, offline, private. What it does, why it matters, how to start.

May 26, 2026

30 SQL Interview Questions for Experienced Professionals

Scenario-based SQL interview questions and answers for professionals with 6–10 years of experience, covering queries, indexing, tuning, transactions, and scale.

March 23, 2025

Most Frequently Asked Java Interview Questions (2025)

29 frequently asked Java interview questions for experienced developers: JVM internals, OOP, collections, exceptions, and multithreading — with answers.

February 15, 2025

React 19 Features for Interviews: Actions, use(), the Compiler, useOptimistic & ref-as-prop

The React 19 features interviewers actually ask about — Actions with useActionState/useFormStatus, the use() hook, the React Compiler's automatic memoization, useOptimistic, ref as a prop (no more forwardRef), and native document metadata — with correct, runnable code.

March 20, 2024

Debouncing in React 19: Correct Hooks, useDeferredValue, and Cancelling Stale Requests

How to debounce user input in React 19 the right way — a correct reusable useDebouncedValue hook, when to reach for useDeferredValue/useTransition instead, and how to cancel stale in-flight requests with AbortController.

March 20, 2024

Two-Way Binding in React: A Typed useBind Hook (and When to Use React 19 Actions Instead)

React has no built-in two-way binding like Angular's ngModel. Build a correct, fully-typed useBind hook that handles text, number and checkbox inputs — and learn when uncontrolled inputs or React 19 form Actions are the better choice.

December 18, 2023

Auto-Migrate Angular Templates to @if / @for: The control-flow Schematic

Angular ships a schematic that rewrites *ngIf and *ngFor to the new @if and @for control flow automatically. The command, what it does (and doesn't) handle, and how to run it safely per-directory.

December 10, 2023

Angular Control Flow (@if / @for / @switch): Syntax, track, and Why It's Faster

Angular's built-in control flow — @if, @for, @switch — replaces *ngIf and *ngFor. Correct syntax (including the mandatory track and the @empty block), why it needs no CommonModule, and the interview points.

December 10, 2023

New Features in Angular 17: A Comprehensive Guide

Angular 17's headline changes: built-in @if/@for/@switch control flow, deferrable views with @defer, and the automatic migration schematic. A full guide.

December 10, 2023

Angular @defer: Lazy-Load Template Blocks with Triggers (@placeholder, @loading, @error)

Angular's @defer block lazy-loads part of a template on a trigger — viewport, interaction, idle, hover or timer — keeping non-critical content out of the initial bundle. Correct syntax, every trigger, prefetching, and the SEO caveat.

December 8, 2023

Creating a Custom Alert in React with TypeScript

Here's a custom alert component without using any external libraries, just using React and TypeScript.

July 25, 2023

Building a Custom React Accordion Inspired by Material-UI

Creating a custom accordion that looks similar to the Material UI (MUI) Accordion can be achieved by adapting the styles to match the Material-UI design.

July 24, 2023

Fix Keras model.fit Failing Under MirroredStrategy (Multi-GPU)

model.fit failing under tf.distribute.MirroredStrategy is almost always: the model/optimizer built outside strategy.scope(), a global batch size that isn't scaled, or a non-replica-aware custom step. The correct pattern, explained.

June 23, 2023

Fix: InvalidArgumentError — 'dtype' bfloat16 Not in List of Allowed Values

This TensorFlow error doesn't mean bfloat16 is invalid — it means the specific op has no bfloat16 kernel. Cast to float32 for that op with tf.cast, or use mixed_bfloat16 precision so Keras places dtypes for you.

June 23, 2023

Fix TensorFlow 'Check failed: work_element_count > 0' (gpu_launch_config.h:129)

This internal TensorFlow crash means a GPU kernel was launched with zero or a negative number of elements — almost always an empty batch, a layer whose shape math collapsed to 0, or an int32 overflow on a huge tensor. Here's how to find which.

June 23, 2023

TensorFlow 'InvalidArgumentError: Graph execution error' — Find the Real Cause

'InvalidArgumentError: Graph execution error' is a generic wrapper — the real cause is in the nested traceback. The three most common ones (shape mismatch, label out of range, dtype mismatch) and how to fix each.

June 22, 2023

Fix CUDA_ERROR_LAUNCH_FAILED & CUDNN_STATUS_INTERNAL_ERROR in TensorFlow

These TensorFlow errors fire after the libraries load, so they're not path problems — usually GPU memory exhaustion (enable memory growth), a cuDNN/CUDA version mismatch, or the GPU being held by another process. How to diagnose and fix each.

June 21, 2023

Could not load dynamic library 'libnvinfer_plugin.so.6' — Harmless TensorRT Warning

This TensorFlow message about libnvinfer_plugin.so is almost always a harmless TensorRT warning, not an error — TF still runs on GPU. When it actually matters, and how to fix it if you need TensorRT.

June 10, 2023

Untraced Functions Warning during Model Saving

The 'Found untraced functions' warning when saving a Keras model is informational, not an error — your model still saves and reloads correctly. Here's why.

June 10, 2023

Fix IDE Auto-Completion Failure for tensorflow.keras

Autocomplete fails for tf.keras because it's a lazily-loaded alias that static analyzers can't follow. Your code still runs — import from keras directly to give the IDE a real module to introspect.

June 8, 2023

Relationship between TF.Slim, TF High-Level API, and Keras

How TF-Slim, the TF high-level API, and Keras relate: three abstraction layers over TensorFlow. TF-Slim is deprecated; use Keras in TensorFlow 2.x today.

June 8, 2023

Fix ImportError: cannot import name 'abs'

This ImportError comes from a shadowed or half-installed package (classically TensorFlow) or a circular import — not from the abs builtin. Here's how to find which one and fix it.

June 8, 2023

Build a CNN for Image Classification with Swift for TensorFlow

Build a CNN for image classification with Swift for TensorFlow (S4TF). Note: S4TF was archived in 2021 — use Python TensorFlow/Keras or PyTorch instead.

June 8, 2023

Fix ImportError: libcublas.so.9.0 cannot open shared object file

This means the dynamic loader can't find the exact CUDA library your framework was built against. The '.9.0' suffix must match exactly — here's how to check whether it's a path problem or a missing CUDA toolkit, and fix each.

June 7, 2023

Fix: Could not load dynamic library 'libcudart.so.11.0'

This TensorFlow message means it needs the CUDA 11.x runtime and can't find it. The '11.0' is a major-version SONAME — any CUDA 11.x provides it, CUDA 12 does not. Here's the triage and fix.

June 7, 2023

How to Change default types globally in tensorflow?

Set TensorFlow's default float type with tf.keras.backend.set_floatx, or use mixed_precision for float16/bfloat16. ConfigProto does not control dtypes.

June 6, 2023

TensorFlow Not Detecting GPU / CUDA Installed via Conda: The Version-Match Fix

TensorFlow returns an empty GPU list even though CUDA is installed via conda — almost always a CUDA/cuDNN version mismatch or a conda-vs-system conflict. Diagnose it and fix it with tensorflow[and-cuda] or a matched conda environment.

June 6, 2023

What are the GPUOptions for Go binding in TensorFlow?

Optimize GPU utilization with TensorFlow's Go binding using GPUOptions. Control memory allocation, growth, and device selection for efficient computations.

June 6, 2023

How to handle class weight for multiple outputs in keras?

Weighting Classes in Multiple Output Models with tf.keras - Custom Loss and Sample Weights Solution

June 6, 2023

How to assign value to a EagerTensor slice?

EagerTensors from tf.constant are immutable, so slice assignment raises AttributeError. Use tf.Variable, or tf.tensor_scatter_nd_update for a modified copy.

June 6, 2023

TensorFlow Lite vs TensorFlow Output: Differences Explained

The advantages of TensorFlow Lite's optimized model size, execution efficiency, and supported operations for mobile and embedded deployments.

June 6, 2023

How to clear GPU memory in tensorflow 2?

Clear GPU memory in TensorFlow 2 by enabling memory growth or setting memory limits. Optimize performance with these simple techniques.

June 6, 2023

Updating Complex/Nested State in Svelte: Stores (immutably) vs Svelte 5 $state

Update nested data in Svelte the right way. With a writable store, use update() and return a new object (immutability keeps reactivity). In Svelte 5, $state is deeply reactive — mutate nested properties directly.

May 26, 2023

What <svelte:fragment> Actually Does (and the Svelte 5 Snippet That Replaces It)

<svelte:fragment> is not a general performance trick — Svelte already allows multiple root elements. It exists to pass several elements into a NAMED slot without an extra wrapper node. In Svelte 5, snippets supersede it.

May 25, 2023

Understanding the Error Handling API in Svelte Components

Svelte error handling: the await catch branch, <svelte:boundary> in Svelte 5, and +error.svelte in SvelteKit. There is no <svelte:error> element.

May 25, 2023

Dynamic Slot Content in Svelte: Why You Can't Set Slots Imperatively (and What to Do Instead)

Svelte slot content is resolved by the parent at compile time — you can't swap it imperatively after a component is created. Drive it with a prop or {#if}, or use Svelte 5 snippets passed as props for a truly reassignable slot.

May 24, 2023

Custom Filter in AG Grid (Angular): A Complete IFilterAngularComp Example

Build a custom AG Grid filter in Angular by implementing IFilterAngularComp — agInit, isFilterActive, doesFilterPass, getModel/setModel — and registering the component on the column. Correct, complete, runnable code.

May 21, 2023

Fix: Unable to Retrieve JDBC Result Set for SELECT * FROM TABLE

The JDBC error 'Unable to retrieve result set' is a generic wrapper. The real cause is almost always an unresolvable table name, a reserved word, a missing SELECT grant, or a closed statement — here's how to tell them apart and fix each.

January 21, 2023

How to convert a date to Unix epoch time in Python?

Convert a date to Unix epoch time in Python with dt.timestamp(). Handle timezones correctly so a naive datetime isn't misread as local time.

January 11, 2023

Fix TypeError: Can Only Concatenate str (Not "NoneType") to str

Fix Python's str and NoneType concatenation error by finding the None value, repairing missing returns, choosing safe defaults, and avoiding common bad fixes.

January 10, 2023

How Inheritance Works in Python: super(), the MRO & Composition vs Inheritance

Python inheritance for interviews: single and multiple inheritance, super() and cooperative __init__, the method resolution order (MRO / C3 linearisation) and the diamond problem, mixins, abstract base classes, and when to favour composition over inheritance.

January 9, 2023

Object-Oriented Programming in Python: Classes, Objects & the Four Pillars (Interview Guide)

A senior-level tour of Python OOP for interviews: classes and objects, __init__ and self, instance vs class vs static methods, @property, dunder methods, @dataclass, and the four pillars — encapsulation, abstraction, inheritance, and polymorphism.

January 9, 2023

Polymorphism in Python: Duck Typing, Dunder Methods & singledispatch (Interview Guide)

How polymorphism really works in Python — duck typing (no shared base class needed), method overriding, operator overloading via dunder methods, functools.singledispatch, and Protocols — with the interview traps around Python's lack of method overloading.

January 8, 2023