What is TLS/HTTPS?

  • HTTPS = HTTP + TLS (Transport Layer Security)
  • Encrypts data between client and server.
  • Provides:
  • Confidentiality – No one can read the data.
  • Integrity – Data can’t be tampered with.
  • Authentication – Confirms site is genuine.

TLS Certificates

  • Issued by a Certificate Authority (CA) (e.g., Let’s Encrypt, DigiCert).
  • Types:
  • DV (Domain Validated) → free, common
  • OV (Org Validated) → verified business
  • EV (Extended Validation) → green bar (rare now)

Get free HTTPS:

# Install Certbot
sudo apt install certbot python3-certbot-nginx

# Generate TLS cert for domain
sudo certbot --nginx -d example.com -d www.example.com

Domains & DNS Basics

  • Domain Name System (DNS): Internet’s phonebook. Converts names → IP addresses.

Common DNS Records

RecordPurposeExampleAIPv4 addressA → 192.0.2.1AAAAIPv6 addressAAAA → 2001:db8::1CNAMEAlias to another domainwww → example.comMXMail servermail.example.comTXTInfo/verificationv=spf1 include:_spf.google.com

Redirect HTTP → HTTPS

Example in Nginx:

server {
    listen 80;
    server_name example.com www.example.com;
    return 301 https://$host$request_uri;
}

Best Practices

  1. Always enable HTTPS everywhere.
  2. Use HSTS (Strict Transport Security):
Strict-Transport-Security: max-age=63072000; includeSubDomains; preload
  1. Use DNS providers with low latency (Cloudflare, AWS Route 53).
  2. Enable DNSSEC for extra protection.

Quiz

Q1: What does TLS provide?

A) Faster load speeds

B) End-to-end encryption and authentication

C) Reduced hosting cost

D) Easier DNS resolution

✅ Answer: B) End-to-end encryption and authentication

Q2: What does an A record in DNS do?

A) Points domain to another domain

B) Stores website SSL certificate

C) Maps domain to IPv4 address

D) Handles email routing

✅ Answer: C) Maps domain to IPv4 address

Monitoring & Observability (Prometheus, Grafana, Sentry)

Difficulty: Intermediate

Description: Learn how to monitor apps with metrics, logs, and error tracking. Use Prometheus for metrics, Grafana for dashboards, and Sentry for error reporting.

Time to read: 12 minutes

Content

Why Monitoring Matters

  • Detect problems early
  • Improve uptime & reliability
  • Debug production issues
  • Optimize performance

Observability Pillars

  1. Metrics → Numeric measurements (CPU, memory, requests/sec).
  2. Logs → Event details (errors, warnings).
  3. Traces → Request journey across services.

Prometheus (Metrics Collection)

  • Time-series database for metrics.
  • Pulls metrics from apps & servers.

Example Node.js Metrics Exporter:

import express from "express";
import client from "prom-client";

const app = express();
const collectDefaultMetrics = client.collectDefaultMetrics;
collectDefaultMetrics();

app.get("/metrics", async (req, res) => {
  res.set("Content-Type", client.register.contentType);
  res.end(await client.register.metrics());
});

app.listen(3000, () => console.log("Metrics at http://localhost:3000/metrics"));

Prometheus scrapes /metrics endpoint regularly.

Grafana (Visualization)

  • Connects to Prometheus, ElasticSearch, Loki, etc.
  • Create dashboards:
  • API latency
  • Error rates
  • System health

Example dashboard panels:

  • CPU Usage (%)
  • Requests per second
  • 95th percentile response time

Sentry (Error Monitoring)

  • Captures runtime errors in frontend/backend.
  • Provides stack traces, user info, breadcrumbs.

Example (Node.js setup):

import * as Sentry from "@sentry/node";

Sentry.init({
  dsn: process.env.SENTRY_DSN,
  tracesSampleRate: 1.0,
});

app.use(Sentry.Handlers.requestHandler());
app.use(Sentry.Handlers.errorHandler());

Best Practices

  1. Use dashboards for system health.
  2. Set up alerts (PagerDuty, Slack).
  3. Collect structured logs (JSON format).
  4. Always monitor user-facing metrics (latency, errors).