AWS
docs.aws.amazon.com › amazon redshift › database developer guide › query performance tuning › query processing › factors affecting query performance
Factors affecting query performance - Amazon Redshift
The query optimizer and the query ... improve query speed. For more information, see Sort keys. Dataset size – A higher volume of data in the cluster can slow query performance for queries, because more rows need to be scanned and redistributed....
Maxon Knowledge Base
support.maxon.net › hc › en-us › articles › 7931985413916-Why-am-I-experiencing-performance-issues-with-Redshift-on-my-Windows-machine
Why am I experiencing performance issues with Redshift on my Windows machine? – Knowledge Base
A driver that both avoids the known memory issue as well as maintains support for OptiX is **Game Ready driver v497.29. You can use a lower driver version, but you will lose support for OptiX. Lower Redshift's Used GPU Memory (%) setting till performance is restored.
What can I do about redshift slowness?
You can find a list of community-submitted learning resources here: https://dataengineering.wiki/Learning+Resources I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns. More on reddit.com
28
43
May 6, 2023amazon web services - Redshift: experiencing slow query performance between 2 segments - Stack Overflow
Hi Bill, I'm replying to your answer as I have a similar issue. The total duration of ingesting procedures increased suddenly, e.g.: the total execution time of the steps takes ~500ms, but the whole call takes 3-4s. The Planning phase is taking longer than before (as per "Database performance" chart in Redshift ... More on stackoverflow.com
performance degradation after Redshift maintenance
I would recommend opening a support ... a known issue. Perhaps there is post-upgrade integrity checks that run for a period or such. Cross Ref: https://repost.aws/questions/QU5L3c0MRASSCZx0euQzlyDA/after-a-redshift-s-maintenance-my-queries-are-too-slow ... Is it possible to check something like "STL_ALERT_EVENT_LOG" to find queries that seem to be slow after the update? This table seems to record query information that may indicate a performance problem, so ... More on repost.aws
2
0
June 19, 2024why does it feel like so many people hate Redshift?
Because it fucking sucks, lol. Basically, it's more expensive and less performative than its competition. Optimization is not trivial, as you have to consider the distribution and sort keys, which are not always intuitive. The user experience is awful too, while you have a very user friendly interface in Snowflake and Databricks with a ton of cool features, in redshift you have a very basic query prompt in AWS console and that's it. It also feels kinda of abandoned by Amazon, it feels the same as when I first used it (2018), while Databricks and Snowflake have new features all the time. More on reddit.com
56
95
May 5, 2025Maxon Knowledge Base
support.maxon.net › hc › en-us › articles › 15763554418204-Why-is-Redshift-rendering-slower-than-expected
Why is Redshift rendering slower than expected? – Knowledge Base
September 5, 2024 - For more complex scenes that require more power, the CPU can become a bottleneck. In such cases, the GPU may finish its tasks quickly, but the render will be delayed while waiting for the CPU to complete its portion.
Integrate.io
integrate.io › home › blog › big data › 15 performance tuning techniques for amazon redshift
15 Performance Tuning Techniques for Amazon Redshift | Integrate.io
November 25, 2025 - Amazon Redshift is a cloud-based data warehouse that offers high performance at low costs. But uneven query performance or challenges in scaling workloads are common issues with Amazon Redshift.
Civis Analytics
support.civisanalytics.com › hc › en-us › articles › 360032992652-Troubleshooting-Redshift-Slowness
Troubleshooting Redshift Slowness – Civis Analytics
November 20, 2023 - This means that if you have more than that number of queries trying to run at the same time, some queries may be queued. Use the query from the Running Queries section of this document to see how many queries are running on your cluster.
AWS re:Post
repost.aws › knowledge-center › redshift-cluster-degrade
Troubleshoot cluster performance issues in Amazon Redshift | AWS re:Post
December 11, 2023 - Monitor your cluster performance metrics. Check the Amazon Redshift Advisor recommendations. Review the query execution alerts and excessive disk usage. Check for locking issues and long-running sessions or transactions.
AWS re:Post
repost.aws › articles › AR58IPQ86FSFOHH42GOTgBlg › amazon-redshift-monitoring-and-troubleshooting-query-performance-using-system-tables
Amazon Redshift: Monitoring and troubleshooting query performance using system tables | AWS re:Post
February 3, 2026 - Performance deviations may indicate workload spikes or cluster/table maintenance-related issues. Consider implementing WLM rules to manage resource-intensive queries and maintain consistent cluster performance.
Reddit
reddit.com › r/dataengineering › what can i do about redshift slowness?
r/dataengineering on Reddit: What can I do about redshift slowness?
May 6, 2023 -
Hi Reddit DE - I'm a data analyst that changed jobs to join a dinosaur working with Redshift. I was previously working with Bigquery for SQL scripts, where just looking at table samples (e.g. SELECT * FROM table LIMIT 5) took microseconds. Under the AWS Redshift architecture, these same table sampling jobs now take 3+ minutes and I'm going crazy.
The admins have set up resources dedicated under a user cluster, so things could be worse, but is there anything small you suggest I push for to make life more bearable? I think I need to start by asking for more 2x, 3x more resource slots, but please stop me if this sounds stupid.
Top answer 1 of 21
58
I work with Redshift and a similar query for me would never take more than a second let alone multiple minutes, so the issue you're seeing strikes me as not inherent to Redshift. Have you raised the issue with the teams who manage those resources? If someone told me it took 3+ mins for SELECT * FROM table LIMIT 5 that would indicate a deeper problem that needed to be solved.
2 of 21
19
Redshift is columnar based so in an instance of select * you’re literally doing the most inefficient thing you could do, because it must scan every column as a file. Redshift shines in areas like incremental aggregation. Anything that requires a lot of small aggregates combined together will perform tremendously better in a columnar based structure than a row based structure like MySQL. But anything that is scanning big data across many columns is awful, even with really efficient indexing. A row based database is good at performing a few large queries. A columnar based database is good at performing many small queries
AWS
docs.aws.amazon.com › amazon redshift › database developer guide › query performance tuning › query analysis and improvement › query performance improvement
Query performance improvement - Amazon Redshift
To fix this issue, you can take a couple of approaches: Run VACUUM on the query tables to re-sort the rows. Review the sort keys on the query tables to see if any improvements can be made. Remember to weigh the performance of this query against the performance of other important queries and ...
Silota
silota.com › amazon redshift guide › monitoring query performance
Monitoring Query Performance · Amazon Redshift Guide · SILOTA
You will usually run either a vacuum operation or an analyze operation to help fix issues with excessive ghost rows or missing statistics. The SVV_TABLE_INFO summarizes information from a variety of Redshift system tables and presents it as a view. Along with STL_ALERT_EVENT_LOG this view can help you understand why your queries have degraded performance either due to the wrong compression encoding, distribution keys or sort styles.
Medium
medium.com › udemy-engineering › improving-amazon-redshift-performance-our-data-warehouse-story-5ec1282c13d8
Improving Amazon Redshift Performance: Our Data Warehouse Story | by Nathan Sullins | Udemy Tech Blog | Medium
December 6, 2018 - Bad queries, poor distribution style and sort key selections, stale statistics and row cruft, insufficient resources, and concurrency and queue configuration issues all affect performance.
Mindful Chase
mindfulchase.com › home › explore › troubleshooting tips › databases › advanced troubleshooting of amazon redshift: fixing query performance, connection, and scaling issues
Advanced Troubleshooting of Amazon Redshift: Fixing Query Performance, Connection, and Scaling Issues - Mindful Chase
March 20, 2025 - High disk I/O usage causing performance degradation. Table scans instead of indexed lookups affecting query speed. Users may experience connection failures due to authentication issues, incorrect security group settings, or network restrictions. Timeout errors while connecting to Redshift from ...
Curate Partners
curatepartners.com › blog › general › avoiding redshift bottlenecks: crucial tuning skills for enterprise-scale performance
Avoiding Redshift Bottlenecks: Crucial Tuning Skills for Enterprise-Scale Performance
June 14, 2025 - This article explores the typical performance bottlenecks in large-scale Redshift deployments and outlines the essential tuning expertise needed to keep your analytics engine running smoothly and efficiently, providing insights for both leaders managing these platforms and the technical professionals responsible for their performance. Before tuning, it’s vital to understand where performance issues typically arise in Redshift’s Massively Parallel Processing (MPP) architecture:
Twilio Segment
segment.com › docs › connections › storage › warehouses › redshift-tuning
Speeding Up Redshift Queries | Twilio
December 2, 2025 - Some databases like Redshift have limited computing resources.
Top answer 1 of 2
1
I would recommend opening a support case to determine if this is a known issue. Perhaps there is post-upgrade integrity checks that run for a period or such.
Cross Ref: https://repost.aws/questions/QU5L3c0MRASSCZx0euQzlyDA/after-a-redshift-s-maintenance-my-queries-are-too-slow
2 of 2
1
Hello.
Is it possible to check something like "STL_ALERT_EVENT_LOG" to find queries that seem to be slow after the update?
This table seems to record query information that may indicate a performance problem, so you may be able to find the query that is causing the problem.
https://docs.aws.amazon.com/redshift/latest/dg/r_STL_ALERT_EVENT_LOG.html
Mindful Chase
mindfulchase.com › home › explore › troubleshooting tips › databases › troubleshooting amazon redshift: common issues and solutions
Troubleshooting Amazon Redshift: Common Issues and Solutions - Mindful Chase
February 27, 2025 - Troubleshoot common Amazon Redshift issues, including connection failures, slow queries, disk space limitations, concurrency bottlenecks, and data loading errors.
Airbyte
airbyte.com › blog › optimize-redshift-performance-and-reduce-costs
How to optimize Redshift performance and reduce costs | Airbyte
November 18, 2022 - For instance, if the percentage of your disk space used goes above seventy-five percent, you will experience performance issues. If your disk space usage exceeds 90%, your cluster performance and stability will reduce drastically.
Reddit
reddit.com › r/dataengineering › why does it feel like so many people hate redshift?
r/dataengineering on Reddit: why does it feel like so many people hate Redshift?
May 5, 2025 -
Colleagues with AWS experience In the last few months, I’ve been going through interviews and, a couple of times, I noticed companies were planning to migrate their data from Redshift to another warehouse. Some said it was expensive or had performance issues.
From my past experience, I did see some challenges with high costs too, especially with large workloads.
What’s your experience with Redshift? Are you still using it? If you're on AWS, do you use another data warehouse? And if you’re on a different cloud, what alternatives are you using? Just curious to hear different perspectives.
By the way, I’m referring to Redshift with provisioned clusters, not the serverless version. So far, I haven’t seen any large-scale projects using that service.
Top answer 1 of 18
139
Because it fucking sucks, lol. Basically, it's more expensive and less performative than its competition. Optimization is not trivial, as you have to consider the distribution and sort keys, which are not always intuitive. The user experience is awful too, while you have a very user friendly interface in Snowflake and Databricks with a ton of cool features, in redshift you have a very basic query prompt in AWS console and that's it. It also feels kinda of abandoned by Amazon, it feels the same as when I first used it (2018), while Databricks and Snowflake have new features all the time.
2 of 18
42
Redshift is annoying to use for a host of reasons. But the simple explanation is that most people that are using it, shouldn't be using it. The main reason people use redshift is not because they do a.gopd analysis of the MPP data warehouse offerings and then land on redshift. It's because redshift is touted as AWS's data warehouse. So if your company uses AWS and you need a data warehouse, it's likely that leadership just chooses redshift, despite the fact it shouldn't really be used in most cases. Check out this white paper for more info. And you can dig deeper into the dozen other white papers there if you are not convinced. I am of the view about 95% of clients using Redshift should not be, and should be on a different database, and the reason they get away with using Redshift is because they do not in fact have Big Data.
Hevo
hevodata.com › home › learn › amazon redshift performance tuning: 4 best techniques
Amazon Redshift Performance Tuning: 4 Best Techniques - Learn | Hevo
December 29, 2022 - Amazon Redshift can deliver 10x ... But even with such processing power, you will find uneven Amazon Redshift Performance by some queries as the data size increases....