Ever wondered how Stripe powers seamless payments for billions of transactions across 100+ currencies for Amazon, Uber & more?

Challenges: global regulatory compliance, real-time fraud detection, massive traffic spikes (Black Friday!), and consistency across distributed databases.

You type “best pizza near me” and Google delivers results in 0.2s. 🍕

How? Google Search works in 4 steps:

- Crawling: Googlebots explore the web, follow links, respect robots.txt
- Indexing: Pages analyzed & catalogued in a massive searchable index

How it works:
Unified data → Payments DB, Capital DB, and custom lists synced asynchronously into Elasticsearch
Cross-index matching → in-memory joins handle fuzzy/multi-source comparisons

How they solve it:
- Client apps request post metadata via the API layer
- API queries Aurora Postgres (partitioned by post_id)
- PgBouncer manages DB connections efficiently
- Metadata stored in JSONB fields → all info in 1 query, no joins
- Kafka CDC ensures writes consistent during migration

Remember when sending money meant IFSC codes & bank forms? 📝

India's UPI changed everything: ₹500 to anyone in 3 seconds using just a phone number. Here's how it works under the hood:

Not a wallet: It's a real-time bank-to-bank infrastructure (345+ banks, 24/7)

How did Instagram scale from 0 → 14M users in just over a year with only 3 engineers?

- Built on Django for rapid iteration, iOS-only launch
- AWS migration: EC2, S3, CloudFront, Elastic Load Balancing
- Data strategy: PostgreSQL + NoSQL, caching with Redis/Memcached, sharding & replication

Ever wonder how Airbnb instantly shows the perfect villa or apartment? 🏖️

Airbnb’s User Signals Platform captures millions of user actions per second: searches, clicks, wishlist saves, and bookings.

Symmetric Encryption → Same key locks & unlocks (fast, used in databases & payments)

Asymmetric Encryption → Public key locks, private key unlocks (secure, powers WhatsApp end-to-end encryption & HTTPS)

Read full article: hw.glich.co/p/what-is-e...

Ever wonder how your chats, payments, and online shopping stay private?

The secret: Encryption. It scrambles your message into unreadable ciphertext while it travels the internet.

Only the person with the right key can unlock it back into readable plaintext.

Programmers: “Comments make code clearer.”
Also programmers:

Another day, another npm supply-chain attack. This time, it's multiple packages totaling ~2 billion downloads

Reliability Through Redundancy:

- Hot-standby Task Managers ready to take over if the primary fails
- Config-based workflows let teams define transforms without deep Flink knowledge
- Batch processing catches anything real-time missed.

No single point of failure

User Segments & Sessions: Platform automatically groups users (active trip planners stay in the segment for 14 days or until booking),

Session windows track short-term behavior patterns. Sliding windows provide continuous insights.

Dynamic categorization at scale

The Flow:

→ User browses listings
→ Events hit Kafka
→ Flink transforms raw events into meaningful signals
→ Stored in a key-value database with append-only writes
→ Other Airbnb services query this data for recommendations.

All under 1 second!

Lambda Architecture Explained:

Speed Layer (Apache Flink) processes events instantly as they happen.

Batch Layer handles historical data for consistency checks, Serving Layer stores processed data for lightning-fast queries.

Best of both: speed + accuracy

Google Search works in 4 main steps:

• Crawling (discovering pages)
• Indexing (organizing info)
• Ranking (ordering results)
• Serving (showing you results).

Each step is a masterpiece of engineering on a massive scale.

Before we dive into Google, let's understand what happens when you visit ANY website.

→ You type a URL
→ Browser does DNS lookup (finds IP address)
→ Establishes TCP connection
→ Sends HTTP request
→ Gets response.

This happens billions of times daily.

Two-Level Load Shedding:

Service-Level: If video catalog is struggling, throttle only those requests
Global-Level: If Zuul itself is overwhelmed, shed traffic across ALL services

This prevents total Netflix outages

The Magic Happens in Zuul (Netflix's API Gateway).

When systems get stressed, Zuul monitors:

• CPU usage
• Concurrent requests
• Connection counts

If thresholds are hit, it progressively drops low-priority requests using a cubic function for smooth scaling