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1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errorsRedis lists are ordered collections that you can grow, read, edit, trim, move, and consume from either end. That two-ended behavior lets one data type implement a stack, a queue, a work handoff, or a bounded event buffer. The core workflow is simple: use LPUSH or RPUSH to add values, LPOP or RPOP to remove them, LRANGE to inspect them, and BLPOP or BRPOP when a consumer should wait for work.
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This guide shows the command choices, their complexity, practical command-line recipes, version qualifications, and the failure modes that matter when lists are used in production.
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How a Redis list works
A Redis list is an ordered sequence stored under one key. Every value has a position, and the list has two addressable ends: the head (the left side) and the tail (the right side). Commands are named for the end they use, so the operation is usually apparent from its name.
| Goal | Head (left) | Tail (right) |
|---|---|---|
| Add an element | LPUSH |
RPUSH |
| Remove an element | LPOP |
RPOP |
| Blocking remove | BLPOP |
BRPOP |
Because insertion and removal can happen at either end, the same list can behave as a last-in, first-out stack, a first-in, first-out queue, or a handoff between two consumers. The key is choosing a consistent pair of ends rather than mixing directions accidentally.
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Check the server version before choosing commands
Redis command documentation is versioned. The command index currently exposes references for Redis 8.10, 8.4, 8.0, 7.4, 7.2, and 6.2, and the version selector on an individual command page should be treated as authoritative for the server you operate. Check the running server before deploying a newer list command:
redis-cli INFO server | grep redis_versionIf your environment does not provide grep, run redis-cli INFO server and read the redis_version field. This matters particularly for list-moving commands: the lists documentation and the LMOVE page identify LMOVE as introduced in Redis 6.2.0, while an 8.8 reference displays a conflicting introduction value. Treat 6.2.0 as the better-supported requirement, but confirm the exact command page for your server. The newer LMOVEM command is described as arriving in Redis 8.10.0, so it should not be assumed to exist on older servers.
Add values with LPUSH and RPUSH
LPUSH: insert at the head
Use LPUSH key element [element ...] when new values belong at the left end. If the key does not exist, Redis creates the list.
LPUSH jobs "compile"Repeated calls place each new value at the head, making LPUSH the natural primitive for a stack. It is also useful when the newest item should be encountered first.
RPUSH: append at the tail
Use RPUSH key element [element ...] to append values at the right end. It also creates the key when it is absent.
RPUSH jobs "compile"
RPUSH jobs "test"
RPUSH jobs "package"With this pattern, the oldest queued item remains at the left while new work arrives at the right. A consumer can then remove from the left with LPOP or BLPOP.
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Be explicit when sending multiple elements
Both push commands accept more than one element in a single call. Treat the command’s end and argument order as part of your data contract, and verify the resulting order with LRANGE key 0 -1 during development. This avoids subtle reversals when a producer changes from one-element calls to batched calls.
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Read a list without removing data
LRANGE: return a range
LRANGE key start stop returns the elements between the supplied offsets, inclusive. Offset 0 is the first element, and -1 denotes the final element, so the complete list is commonly inspected with:
LRANGE jobs 0 -1LRANGE runs in O(S+N), where S is the distance of the start offset from the nearest end and N is the number of elements returned. A full-list read therefore costs in proportion to the amount returned; avoid repeatedly fetching a very large list when a small window is sufficient.
LLEN: get the length
LLEN key returns the number of elements in the list in O(1). Use it for queue-depth checks, metrics, or a quick guard before displaying a list. Length is metadata, so it does not require scanning every value.
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LINDEX key index reads one element by zero-based index. Access at the first or last element is O(1); an index in the middle is O(N). Negative indexes count backward from the tail, which is useful for looking at the newest entries without first calculating the length.
LINDEX jobs 0
LINDEX jobs -1
LINDEX jobs 10Use LINDEX for occasional positional inspection, not as a substitute for a random-access database structure. A workload that constantly reads arbitrary middle positions is a signal to reconsider the data type or maintain a separate index.
Remove elements from a list
LPOP and RPOP: non-blocking removal
LPOP key removes and returns an element from the head. RPOP key does the same at the tail. Pairing LPUSH with LPOP creates a stack; pairing RPUSH with LPOP creates a queue.
RPUSH tasks "one"
RPUSH tasks "two"
LPOP tasks
LRANGE tasks 0 -1Use these commands when an empty list should be handled immediately by the client. For a consumer that should wait instead of polling, use a blocking pop.
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LREM key count element removes occurrences of a value from a list. The count controls how many matching elements are targeted and from which direction, so document the chosen count convention in application code. Redis deletes the list key if removing the final element leaves no list entries.
LREM is value-based rather than position-based. If two jobs share the same serialized value, removing one by value may affect an unintended occurrence; use a unique identifier in each list element when individual identity matters.
Trim a list deliberately with LTRIM
LTRIM key start stop keeps only the selected inclusive range and removes everything outside it. As with LRANGE, negative offsets count from the end and -1 means the last element.
LTRIM recent-events 0 99The example keeps the first 100 elements. To retain the newest 100 entries after appending at the tail, use a range ending at -1 and beginning at -100:
LTRIM recent-events -100 -1LTRIM has complexity O(N), where N is the number of elements removed. It is therefore well suited to bounded buffers when trimming discards a relatively small amount on each write. If a trim routinely removes a very large portion of a list, measure the resulting latency and schedule that work appropriately.
A common bounded-buffer sequence is:
RPUSH recent-events "$event"
LTRIM recent-events -1000 -1This keeps the list at roughly the latest 1,000 events. The two commands should be issued through the same application workflow, and callers should account for concurrent writers if exact ordering or an exact maximum is critical.
Update or search by position and value
LSET: replace one indexed element
LSET key index element replaces the value at an existing index. Like LINDEX, it is O(1) at the first or last element and O(N) for a middle position.
LSET jobs 0 "running"
LSET jobs -1 "complete"LSET is useful for small status markers in a known position. It is not a general-purpose in-place update mechanism for large, frequently edited records; rewriting a serialized record or using a hash keyed by an item identifier may be a better design in that case.
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LPOS: find matching values
LPOS key element [RANK rank] [COUNT num-matches] [MAXLEN len] searches for positions containing a value. The optional arguments let you select a ranked match, request multiple matches, or cap how much of the list is examined.
LPOS jobs "compile"
LPOS jobs "compile" COUNT 3 MAXLEN 1000Use LPOS when the value itself is the search key. If values are structured documents, make the searchable identifier explicit and keep the representation consistent so equality checks are predictable.
Move items between lists with LMOVE
LMOVE source destination <LEFT | RIGHT> <LEFT | RIGHT> removes an item from one end of the source list and pushes it onto one end of the destination list. The first direction names the source end; the second names the destination end.
LMOVE pending processing LEFT RIGHTThis pattern takes the oldest item from the left of pending and places it at the right of processing. Other combinations support stack-like transfers, such as right-to-left or left-to-left movement.
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Use blocking pops for waiting consumers
BLPOP: wait for the first available list
BLPOP key [key ...] timeout checks the listed keys in the order supplied and removes an element from the first non-empty list. A timeout of 0 waits indefinitely.
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BLPOP high-priority normal 30The consumer waits up to 30 seconds for work, checking high-priority before normal. With:
BLPOP high-priority normal 0the connection remains blocked until an item becomes available. Redis documentation describes BLPOP and BRPOP as blocking the connection until the timeout is reached or another client pushes an item.
BRPOP: the tail-oriented counterpart
BRPOP follows the same blocking model but removes from the right end. Choose BLPOP or BRPOP to match the producer’s push direction and the ordering your consumer requires.
Design the connection around blocking behavior
A connection waiting in BLPOP or BRPOP cannot simultaneously serve unrelated commands. Use a dedicated consumer connection or a client-pool connection reserved for blocking operations. Set a finite timeout when the worker must periodically perform health checks, refresh configuration, or shut down cleanly; use timeout 0 only when indefinite waiting is intentional.
Choose a list pattern
| Use case | Producer | Consumer | Result |
|---|---|---|---|
| Stack | LPUSH |
LPOP |
Newest item is processed first. |
| FIFO queue | RPUSH |
LPOP |
Oldest item is processed first. |
| Blocking FIFO queue | RPUSH |
BLPOP |
Consumer waits instead of polling. |
| Tail-consuming stack | RPUSH |
RPOP |
Newest item at the tail is processed first. |
| Bounded recent-items buffer | RPUSH then LTRIM |
LRANGE |
Only the chosen window is retained. |
| List handoff | LMOVE |
One operation transfers an item between two lists and chosen ends. | |
Complexity at a glance
| Command | Primary job | Complexity stated in the Redis references | Operational implication |
|---|---|---|---|
LPUSH, RPUSH |
Add at an end | Not stated in the supplied command summary | Use for end-oriented ingestion. |
LPOP, RPOP |
Remove at an end | Not stated in the supplied command summary | Use for immediate, non-blocking consumption. |
LRANGE |
Read a range | O(S+N) | Start near an end and return only what is needed. |
LLEN |
Read length | O(1) | Suitable for frequent depth checks. |
LINDEX |
Read one index | O(N), O(1) at first or last | Middle-index access can become expensive. |
LSET |
Replace one index | O(N), O(1) at first or last | Prefer end positions or another data model for heavy random updates. |
LTRIM |
Keep a range | O(N), where N is removed | Trim in bounded batches when possible. |
Troubleshoot common list problems
Items appear in the wrong order
- Confirm whether producers use LPUSH or RPUSH.
- Confirm whether consumers use the matching left or right pop.
- Inspect the actual sequence with
LRANGE key 0 -1rather than inferring it from application logs. - When batching multiple values, test the resulting order explicitly before rolling the change out.
A consumer spins while no work exists
Polling with LPOP or RPOP requires the client to decide how often to retry. Replace the polling loop with BLPOP or BRPOP when waiting is acceptable. Use a finite timeout if the worker must regain control periodically, and reserve a dedicated connection for the blocking call.
A list grows without bound
Decide whether the data is a queue, a retained history, or an accidental backlog. For a fixed recent window, append with RPUSH and apply LTRIM using negative offsets. For a queue, monitor LLEN and investigate producer-consumer imbalance rather than trimming work that has not been processed.
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Middle operations are slow
LINDEX and LSET are only constant-time at the ends. If the application repeatedly searches, edits, or reads the middle of a large list, move that access pattern to a structure designed for it, or maintain a separate lookup keyed by the item identifier.
A command fails on one environment
Compare the server versions, not just client-library versions. Use the Redis command page’s version selector for the deployed release. LMOVE should be checked against the 6.2.0 requirement, and LMOVEM should be treated as an 8.10.0-era feature until verified on the target server.
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A practical implementation checklist
- Define the ordering contract: newest-first, oldest-first, or no ordering guarantee beyond one end.
- Select the producer and consumer ends, then encode that choice in command names and tests.
- Use LRANGE for bounded inspection and LLEN for depth metrics; avoid full-list reads by default.
- Use LPOP/RPOP for immediate attempts and BLPOP/BRPOP for waiting workers.
- Apply LTRIM only when discarding outside a deliberate retention window.
- Use LINDEX, LSET, and LPOS with awareness that middle access is not constant-time.
- Check the Redis server version before adopting LMOVE or newer list commands.
- Give blocking consumers dedicated connections and define a shutdown or timeout policy.
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