ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

NoSQL, Couchbase, MongoDB. Fast but can we compensate?

Updated on August 5, 2015

The NoSql movement has picked up in the last 10 years with the rising popularity of the Internet.

With the creation of large amounts of unstructured data, consistency isn’t that important considering that a lot of what is being written to these databases is just content like blog posts and tweets.

The real requirement for NoSql databases is to support tens of millions of users. The compromises they make for scalability and performance will seldom affect their users in any noticeable way.

NoSql technologies when paired with a data cache (Couchbase = Memcached + Couchdb) offer available and low latency solutions, but they do so by relaxing consistency

Couchbase and mobile


When deciding what data store to use in your next application, if availability or low latency is on the list of important quality attributes, you had best think twice.

When considering this type of technologies;

  • first pick the processes that are suitable candidates
  • ask the question 'How do you intent to compensate in the case of inconsistency?'
  • realise that the decision of where to use this technology may be constrained by the ability and willingness of the business to compensate.

Available and fast

An example of this is when sells books, say they are using a cluster of machines to hold the state of the warehouse and they update that state when purchases occur, they are highly available and fast.

If for any reason one if the machines is unable to communicate with the others (a partition forms), or misses an update, that version of the state may differ from what is actually available.

If a customer was served information out of one these machines with 'stale' data, the potential to sell something that one does not have stock of exists.

This is both good and bad, on the good side, the shop is open and you are taking sales, you are perceived to be available and fast (low latency), on the bad side you have just sold a thing you do not have in stock.


SQL technologies value consistency over all, while they can be clustered it requires special expertise and one rarely finds large clusters of hundreds of machines.

SQL technologies value consistency so much that they trade-off availability and low latency in any case where consistency may be compromised.

An example of this can be seen when calls get queued up while waiting for locks to be released, the database prefers to make callers either wait (high latency) or time out (unavailability) in periods of high load rather than risk any inconsistency in the data.

This is both good and bad, on the good side, the shop will never sell anything it does not have, but on the bad side you may miss sales and frustrate customers in high load scenarios.


A good way to remember this is PACELC. PACELC reads as ‘When a partition forms choose between being available or being totally consistent in all other cases choose between low latency and consistency’

Can we compensate?

In deciding to use a NoSql technology designers should seek to discover how good a fit the business process is to that technology. The best question to ask of business is 'How do you intend to compensate in the case of inconsistency?'

In the example above,, on discovering the inconsistency could contact the client, admit the mistake and offer a voucher on the next purchase and place an express order to get it to them as soon as they can, most of us would be happy with such an outcome.

No room at the hospital

In the research I did for a hospital, who were looking at using NoSql technologies to back the admissions process I asked if they could compensate?

It turned out no, if there are no beds available in the hospital and a sick person arrives due to a consistency mistake, they cannot add more beds into the hospital, and send that sick person on a road trip to the nearest hospital in the group with a bed.

Enterprise Scenarios

Some enterprise scenarios that I can think of are;

  • reading enterprise wide static data out of a NoSql backed in-memory cluster of machines, this makes sense as the data does not go stale often, and the resource needs the high availability and low latency characteristics
  • backing a payment/financial system with NoSql technologies, what is the impact of the customer not seeing the payment reflected immediately?, or what does it mean if a transaction is not included in the invoicing run due to a consistency issue?, it depends on your situation, but at least you have asked the right questions.

Important points

So when considering this type of technologies;

  • first pick the processes that are suitable candidates
  • ask the question 'How do you intent to compensate in the case of inconsistency?'
  • realise that the decision of where to use this technology may be constrained by the ability and willingness of the business to compensate.


    0 of 8192 characters used
    Post Comment

    No comments yet.


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)