🚀 I wanted to know: Which database inserts 1M records faster—MongoDB or PostgreSQL?

So I built a benchmark pipeline from scratch—and the results surprised me.

💡 Why I Built This

I've always loved both Mongo and Postgres. But when it comes to high-volume writes...

💭 Which one actually performs better?

To find out, I created a controlled benchmark:

  • Installed both on Docker locally
  • Used realistic e-commerce data
  • Ran single, batch, and concurrent insert tests
  • Collected performance data: insert speed, CPU, memory

🧪 Step 1: Generate Realistic Data

I used Python + Faker to simulate real-world e-commerce activity:

  • 50,000 customers
  • 50,000 products
  • 900,000 orders

Each record includes nested objects, timestamps, and varied fields. Think: preferences, inventory, shipping, JSON blobs.

python data_generator.py --customers 50000 --products 50000 --orders 900000

🛠️ Step 2: Run the Benchmark

I tested 3 insertion styles for both Mongo and Postgres:

  1. Single inserts – one record at a time
  2. Batch inserts – 100 to 10,000 records per operation
  3. Concurrent inserts – up to 8 threads with batching

Metrics collected:

  • 🕐 Elapsed time
  • 🔁 Records per second
  • 🧠 CPU usage
  • 📦 Memory usage

⚔️ What I Found

🚀 Overall Performance

Database Avg Throughput (records/sec)
MongoDB 46,012
PostgreSQL 8,900

MongoDB was 5.17x faster on average.

📦 Batch Inserts (Customers)

mongo vs postgresql Batch Inserts

  • MongoDB peaked at 78K/sec
  • PostgreSQL topped at 29K/sec

Batching unlocks massive gains for both—but Mongo scales faster.

🧵 Concurrent Inserts (Orders)

mongo vs postgresql Concurrent Inserts

  • MongoDB: 38K → 110K/sec (with 8 threads)
  • PostgreSQL: 14.6K/sec (plateaus early)

Mongo loves parallelism. Postgres has limits here.

🔍 Single Inserts

mongo vs postgresql Single Inserts

  • PostgreSQL wins in single insert performance
  • Its row-level optimization outperforms Mongo’s write path

⚙️ Resource Usage

mongo vs postgresql Resource Usage

  • Postgres used less CPU & memory overall
  • Mongo burned hotter under concurrency

🧠 TL;DR: Who Wins?

Category Winner
🏎️ Overall Speed MongoDB
🎯 Single Inserts PostgreSQL
📦 Batch Scaling MongoDB
🧵 Concurrency Scaling MongoDB
💡 Resource Efficiency PostgreSQL

🔧 If you need blazing speed, go MongoDB.

🛡️ If you need strict schema & efficiency, go PostgreSQL.

🧪 Try It Yourself (GitHub Repo)

Want to run your own tests?

# Clone the project
git clone https://github.com/hassancs91/mongo-vs-postgres
cd mongo-vs-postgres-benchmark

# Start databases
docker run -d --name mongo -p 27017:27017 mongo
docker run -d --name postgres -e POSTGRES_PASSWORD=postgres -p 5432:5432 postgres

# Generate data
python data_generator.py --customers 50000 --products 50000 --orders 900000

# Run benchmarks
python benchmark.py --data-dir data --output-dir results --postgres-host localhost ...

# Generate report
python report_generator.py --results-dir results --output-file results/case_study_report.md --charts-dir results

📁 You’ll get:

  • JSON results
  • PNG charts
  • Full Markdown report

🔭 What I'm Testing Next

  • Complex query performance (joins, aggregations)
  • Updates and deletes
  • Mixed workloads (read + write)
  • 10M+ record datasets

💬 Let’s Talk

Which database has performed better for you in real-world write-heavy apps?

Have you ever hit a scaling wall with one of them?

I'd love to hear your stories 👇

📥 Full report + visuals + code:

👉 https://github.com/hassancs91/mongo-vs-postgres

🧑‍💻 Happy benchmarking!