Redis with Java (Jedis, Lettuce) - Time & Space Complexity

Time Complexity: Redis with Java (Jedis, Lettuce)

O(n)

Understanding Time Complexity

When using Redis with Java clients like Jedis or Lettuce, it is important to understand how the time cost of commands grows as data size increases.

We want to know how the number of operations changes when we run commands on Redis through Java.

Scenario Under Consideration

Analyze the time complexity of the following Redis commands executed via Java.

// Using Jedis client in Java
Jedis jedis = new Jedis("localhost");

// Add 1000 items to a Redis list
for (int i = 0; i < 1000; i++) {
    jedis.lpush("mylist", "value" + i);
}

// Retrieve all items
List<String> items = jedis.lrange("mylist", 0, -1);
    

This code pushes 1000 values into a Redis list and then fetches all items from it.

Identify Repeating Operations

Look at what repeats in this code.

• Primary operation: The loop calls lpush 1000 times to add items.
• How many times: Exactly 1000 times for pushing, then one lrange to get all items.

How Execution Grows With Input

As the number of items to add grows, the number of lpush calls grows the same way.

Input Size (n)	Approx. Operations
10	10 lpush calls + 1 lrange
100	100 lpush calls + 1 lrange
1000	1000 lpush calls + 1 lrange

Pattern observation: The number of lpush calls grows directly with input size, while lrange is a single call but returns all data.

Final Time Complexity

Time Complexity: O(n)

This means the total time grows linearly with the number of items you add or retrieve.

Common Mistake

[X] Wrong: "Calling lpush multiple times is just one operation because it's the same command repeated."

[OK] Correct: Each lpush call is a separate network request and Redis operation, so the total time adds up with each call.

Interview Connect

Understanding how Redis commands scale when used from Java clients helps you explain performance in real projects and shows you can reason about backend efficiency.

Self-Check

What if we used a Redis pipeline to send all lpush commands at once? How would the time complexity change?