Sergey Leschev

Team Lead | CTO

Swift (L6+) | Full Stack (L6+) | Design Patterns (L6+) | System Architect (L7+) | Blog

Google Engineering Level: L7+

🏆 Awards

Ranking #Dev: Global TOP 200 (Certificate)

Languages: Swift, TypeScript, Shell, Database (T-SQL, PL/SQL, MySQL).

Algorithms: linked lists, binary search, hash table, queue/stack, dfs/bfs, sort, heap/hash, two pointers, sliding window, tree, greedy problems etc.

🚀 Developer Roadmap

S.Leschev iOS Developer (Google Engineering Level: L6+) Roadmap.
S.Leschev FullStack Developer (Google Engineering Level: L6+) Roadmap.
S.Leschev Responsive Email Design (Google Engineering Level: L6+) Roadmap.
S.Leschev Design Patterns (Google Engineering Level: L6+) Roadmap.
S.Leschev System Architect (Google Engineering Level: L7+) Roadmap.

💻 Technologies

Tech Stack (L7+)

Swift [4, 5+, UIKit, Autolayout, UIKitPlus, GCD/Operations/Concurrency 5.5+, Alamofire, ObjectMapper, SwiftLint, SwiftGen, FP, pre/after-main opt], SwiftUI [iOS, watchOS, Widgets, App Clips], Apple TV/AirPlay [Composition, Secondary Display], Realm, Lottie, JWT, CryptoSwift, RxSwift, REST, Firebase, Java [7-8], PWA, Angular [2-6+], Ionic Framework [3-5+], React Native [Redux, MobX], JavaScript, React [Next.JS; Redux, Redux Tookit +Slice/Immer, Prime React], CSS [scss], Node.js [10x Express/SQL;14x NestJS 6;7+/TypeORM], TypeScript (+ESLint, Jest), C#, .Net Core [1-3+], MS SQL [2016+], SQL, Objective-C, MongoDB [3.6, 4.4, Config, Replication, Sharding], RabbitMQ, GraphQL [Schemas; Resolver; Request; Validation; Queries&Mutations; Apollo; Reactive], Apache Kafka, Mockapi, Mac Os, iOS [10;12;13;14+], Android, OneSignal, Localization (Phrase/json/i18next), Zeplin, Figma, Sketch.

Analytics (L6+)

Tableau, Amplitude [SDK], AppsFlyer [SDK 5, 6+, Raw Data, Data Locker, Protect360, web-2-app, People-Based Attribution (PBA), Conversion Path, OneLink], Facebook for Business [SDK, Graph, Conversions Api, Pixel, Reports], Snapchat, TikTok, Google Tag Manager (GTM), Google Analytics [GA4;UA], Apple SKAd (+PCM), Qlik, Yandex, Hotjar, SplitMetrics, Apphud, Appfollow, A/B testing, Airflow, Airbyte, Qonversion.

Infra/DevOps (L6+)

CI/CD tools [XCode Cloud, Github Actions/DO, Jenkins, Codemagic, Gitlab, AWS CodeBuild], Git [+Flow], Chromium + Transporter, Instana, Freshworks, Docker [+compose], Twilio, Zapier, Linux [+ssh, iptables, Ubuntu 16/18/20+, snap/apt/npm/yarn/brew], Amazon Web Services (AWS), Digital Ocean (DO), GRE, IPSEC, VPN, Cloudflare [DNS, CDN, SSL, Guard, Rules], Crashlytics, Grafana, Sentry, RayGun, Nginx, Let’s Encrypt [SSL], Win Server [+PowerShell], IIS, Pingdom, UptimeRobot, Apache JMeter, PAW, Postman, Charles Proxy, Indigo Browser, Published Apps [Apple AppStore, Google Play, Amazon Appstore, Huawei AppGallery, Galaxy Store, Snapcraft].

Payment Providers (L6+)

Apple StoreKit [+Retention, Sales Reports], Stripe [nest-SDK, node-SDK, Stripe Checkout, Stripe Elements, Stripe Prebuilt Page, Stripe via iframe, Sigma SQL Financial Reports], PayPal [SDK], high-risk processing providers [Solid Payments, Recurly, SolidGate, Braintree], CloudPayments, DCB (fortumo), Paymentwall, SafeChange, CCBill, Klarna, Pikassa, Paymentwall, Exactly, Realisto, Cypix, Payselection.

DeFi

Web 3.0: Solidity, Javascript, Hardhat, REMIX, Ethers.js, Ganache, TypeScript (react.js, node.js).

Solidity (Consensys, Alchemy), Metamask, SafePal, Launchpad, PancakeSwap (BNB), Uniswap (ETH), Dextools/PooCoin, Gas/gwei Optimization, Front-Runner Bots, Slippage Optimization, CEX/DEX, Binance Smart Chain (BNB), Ethereum (ETH), Polygon (Matic), Tokens List [Coinmarketcap;CoinGecko].

Auth Providers (L6+)

Apple ID, Google, Facebook (Meta), Fitbit.

Support Services (L6+)

Intercom, Hiver, ChargeBee, HelpShift, HelpCrunch, Freshchat.

Reports (L6+)

P&L, CF, Key metrics, Unit-economics [AARRR, RARRA], Cohort analysis.

PM Stack (L7+)

Agile [Scrum, Kanban, +V&E +ICE +RICE, PRINCE2], Driven Development [TDD, BDD/QUICK, DDD, FDD], ISTBQ, Clickup, Jira, Confluence, Notion, Asana, Team Foundation (TFS), Miro, diagrams.net/ERD, Microsoft Project, OmniPlan, UML [IBM Rational Rose, Visio], Reetro.

React Custom Hooks (L6+)

useArray useAsync useClickOutside useCookie useCopyToClipboard useDarkMode useDebounce useDebugInformation useDeepCompareEffect useEffectOnce useEventListener useFetch useGeolocation useHover useLongPress useMediaQuery useOnlineStatus useOnScreen usePrevious useRenderCount useScript useStateWithHistory useStateWithValidation useStorage useTimeout useToggle useTranslation useUpdateEffect useWindowSize

Design Patterns (L6+)

Behavioral	Creational	Structural
🐝 Chain Of Responsibility	🌰 Abstract Factory	🔌 Adapter
👫 Command	👷 Builder	🌉 Bridge
🎶 Interpreter	🏭 Factory Method	🌿 Composite
🍫 Iterator	🔂 Monostate	🍧 Decorator
💐 Mediator	🃏 Prototype	🎁 Facade
💾 Memento	💍 Singleton	🍃 Flyweight
👓 Observer		☔ Protection Proxy
🐉 State		🍬 Virtual Proxy
💡 Strategy
🏃 Visitor
📝 Template Method

Project Guidelines (L6+)

A set of best practices in my projects.

🏫 Education

Belarusian State University

2004 – 2009

Faculty of Applied Mathematics & Informatics.

Computer science / Mathematician-system programmer.

🏆 Awards

Golden Award for the Year of the Tiger Challenge

Algorithmic skills: Dynamic programming, Greedy algorithms, Catepillar method, Binary search algorithm, Fibonacci numbers, Euclidean algorithm, Sieve of Eratosthenes, Prime and composite numbers, Maximum slice problem, Stack and Queues, Sorting, Time Complexity, Arrays, Prefix Sums, Leader, etc.

Contest: Algorithms, SQL, Data Structures, Bitwise operations (bit-ops), Frontend.

Licenses & certifications

🏆 LeetCode Global TOP 200 (Swift: Certificate, Sources: Swift, Sources: TypeScript).
🏆 Golden Award for the Year of the Tiger Challenge (Swift: Certificate, Sources: Swift).
🏆 Golden Award Muad’Dib’s Challenge (Swift: Certificate, Sources: Swift).
2022 July LeetCode Challenge (2022-07-31).
2022 June LeetCode Challenge (2022-06-30).
2022 May LeetCode Challenge (2022-05-31).
2022 Apr LeetCode Challenge (2022-04-30).
LeetCode Dynamic Programming (2022-05-07).
Graph Theory (2022-04-30).
SQL (2022-04-26).
Algorithm I (2022-04-30), Algorithm II (2022-05-21).
Data Structure I (2022-04-30), Data Structure II (2022-05-21).
Binary Search I (2022-04-28), Binary Search II (2022-05-18).
Programming Skills I (2022-04-28), Programming Skills II (2022-05-18).
 Health & Fitness iOS App / Fitness Motivation / AppStore (Website: motivations.coach, Sources: SwiftUI) @ S. Leschev.
 Social Network iOS App / Social Network / AppStore / Sources: SwiftUI @ S. Leschev.
 Utility MacOS App / Calc-It / Core / AppStore (Sources: Swift) @ S. Leschev.
Facebook Blueprint, Snap Inc, Bytedance, AppsFlyer (Marketing SDK), Google Analytics (SDK, GA4, UA).
Internet Initiatives Development Fund (IIDF / Economics).
Stanford University (Swift: UIKit, SwiftUI).
Coursera (Swift): Best Practices For iOS User Interface Design, Networking And Security in iOS Applications.
Zdes i Sejchas Consulting Group (Professional Management Skills, Agile Methodologies).
LinkedIn Skill Asessment (Mobile): Swift (Programming Language), Object-Oriented Programming (OOP), Objective-C, C++, Ionic, JSON, XML, Android, Kotlin, Maven, Java, REST APIs.
LinkedIn Skill Asessment (Front-End): Front-end Development, Angular, React, Javascript, HTML, CSS (scss), jQuery.
LinkedIn Skill Asessment (Back-End): Node.js, Java, Spring Framework, Scala, C#, .NET Framework, Unity, Python (Programming Language), Django, PHP, C (Programming Language).
LinkedIn Skill Asessment (Databases): MongoDB, NoSQL, Transact-SQL (T-SQL), MySQL.
LinkedIn Skill Asessment (Infra/DevOps): Bash, Git, Amazon Web Services (AWS), AWS Lambda, Google Cloud Platform (GCP), Microsoft Azure, Hadoop, IT Operations.
LinkedIn Skill Asessment (AI): Machine Learning, MATLAB, Python AI, R (Programming Language).

🏆 Awards

Golden Award Muad’Dib’s Challenge

Algorithmic skills: Dynamic programming, Greedy algorithms, Binary search, Stack and Queues, Sorting, Time Complexity.

Contest: Algorithms, Data Structures.

Languages: Swift.

Contacts

I have a clear focus on time-to-market and don't prioritize technical debt. And I took part in the Pre-Sale/RFX activity as a System Architect, assessment efforts for Mobile (iOS-Swift, Android-Kotlin), Frontend (React-TypeScript) and Backend (NodeJS-.NET-PHP-Kafka-SQL-NoSQL). Moderator of DEV Community. And I also formed the work of Pre-Sale as a CTO from Opportunity to Proposal via knowledge transfer to Successful Delivery.

🛩️ #startups #management #cto #swift #typescript #database

📧 Email: sergey.leschev@gmail.com

👋 LinkedIn: https://linkedin.com/in/sergeyleschev

👋 Twitter: https://twitter.com/sergeyleschev

👋 Github: https://github.com/sergeyleschev

🌎 Website: https://sergeyleschev.github.io

🌎 DEV Community (moderator): https://dev.to/sergeyleschev

🌎 Reddit: https://reddit.com/user/sergeyleschev

🌎 Quora: https://quora.com/sergey-leschev

🌎 Medium: https://medium.com/@sergeyleschev

🖨️ PDF: Download

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