Revenue Recognition During each of the years ended December 31, 2019 , 2018 , and 2017 , the Company derived more than 95% of its revenue from recurring revenue streams, consisting primarily of (1) colocation, which includes the licensing and leasing of cabinet space and power and (2) connectivity services, which includes cross-connects, broadband services, and external connectivity. The remainder of the Companys revenue is from non-recurring revenue, which primarily includes installation services related to a customers initial deployment. The majority of the Companys revenue contracts are classified as licenses and accounted for in accordance with Accounting Standards Codification (ASC) 606, Revenue from Contracts with Customers (ASC 606), with the exception of certain contracts that contain lease components and are accounted for in accordance with ASC 842, Leases (ASC 842). The Company recognizes revenue when control of these goods and services is transferred to its customers in an amount that reflects the consideration it expects to be entitled to in exchange for those goods and services. Revenue from recurring revenue streams is generally billed monthly and recognized using a time-based measurement of progress as customers receive service benefits evenly throughout the term of the contract, which is generally three to five years. Non-recurring installation fees, although generally paid in a lump sum upon installation, are deferred and recognized ratably over the contract term, determined using a portfolio approach. Non-recurring installation fees are not assessed as performance obligations as they are determined to be immaterial in the context of the contract with the customer. Revenue is generally recognized on a gross basis as a principal versus on a net basis as an agent, largely because the Company is primarily responsible for fulfilling the contract, takes title to services, bears credit risk, and has discretion in establishing the price when selling to the customer. For contracts with customers that contain multiple performance obligations, the Company accounts for individual performance obligations separately if they are distinct or as a series of distinct obligations if the individual performance obligations meet the series criteria. Determining whether products and services are considered distinct performance obligations that should be accounted for separately versus together may require significant judgment. The transaction price of a contract is allocated to each distinct performance obligation on a relative standalone selling price basis. The standalone selling price is determined by maximizing observable inputs such as overall pricing objectives, customer credit history, and other factors. Other judgments include determining if any variable consideration should be included in the total contract value of the arrangement, such as price increases. Any variable consideration included in the total contract value of the arrangement is allocated to each distinct obligation, or series of distinct obligations, in an amount that depicts the consideration to which the Company expects to be entitled in exchange for transferring the underlying goods or services to the customer. The Company has also made the accounting policy election to exclude taxes assessed by a governmental authority that are both imposed on and concurrent with a specific revenue-producing transaction and collected by the Company from a customer from its measurement of the transaction price. Occasionally, the Company enters into contracts with customers for data center space and office space, which contain lease components. The Companys leases with customers are generally classified as operating leases and lease payments are recognized on a straight-line basis over the lease term. Lease revenue related to data center space is included within colocation revenue, while lease revenue related to office space is included within other revenue. The Company guarantees certain service levels, such as uptime, as outlined in individual customer contracts. If these standard service levels are not achieved, the Company would reduce revenue for any credits given to the customer as a result. There were no service level credits issued during the years ended December 31, 2019 , 2018 , and 2017 . Contract Balances The Company generally invoices customers in monthly installments payable in advance. The difference between the timing of revenue recognition, and the timing of billings and cash collections results in the recognition of accounts receivable, contract assets, and deferred revenue (contract liabilities) on the consolidated balance sheets. Receivables are recorded at invoice amounts, net of allowance for doubtful accounts, and are recognized in the period when the Company has transferred goods or provided services to its customers, and when its right to consideration for that transfer is unconditional. Payment terms and conditions vary by contract type, although terms generally include a requirement of payment within 15 to 30 days of the invoice date. In instances where the timing of revenue recognition differs from the timing of invoicing, the Company has determined that its contracts generally do not include a significant financing component. The Company assesses collectability based on a number of factors, including past transaction history with the customer and the creditworthiness of the customer. A contract asset exists when the Company has transferred products or provided services to its customers, but customer payment is contingent upon future satisfaction of a performance obligation. Certain contracts include terms related to price arrangements and allocations of consideration to multiple performance obligations recognized over differing periods of time. The Company generally recognizes revenue ratably over the contract term, which could potentially give rise to contract assets during certain periods of the contract term. Deferred revenue represents amounts that are recognized when the Company has an unconditional right to a payment, which has been either billed to, or collected from, customers prior to transferring control of the underlying good or service to the customer. The opening and closing balances of the Companys contract assets and deferred revenue are as follows: Contract assets, current portion (1) Contract assets (2) Deferred revenue, current portion Deferred revenue (in thousands) January 1, 2019 $ 145 $ 2,845 $ 12,322 $ 18,084 December 31, 2019 496 3,216 14,991 27,852 Increase $ 351 $ 371 $ 2,669 $ 9,768 ________________________________________ (1) Contract assets, current portion are included within other current assets of the Companys consolidated balance sheet as of December 31, 2019 . (2) Contract assets are included within other assets of the Companys consolidated balance sheet as of December 31, 2019 . The differences between the opening and closing balances of the Companys deferred revenue primarily result from timing differences between the Companys satisfaction of performance obligations and associated customer payments. Revenue recognized during the year ended December 31, 2019 from the opening balance of deferred revenue was $12.5 million . For the year ended December 31, 2019 , no impairment losses related to contract balances were recognized on the consolidated statement of comprehensive income (loss). Contract Costs Contract costs include the Companys incremental direct costs of either obtaining or fulfilling a contract, which primarily consist of sales commissions and bonuses. Contract costs are deferred and amortized on a straight-line basis over the estimated period of benefit. The Company elected to apply the practical expedient to expense contract costs when incurred if the amortization period is one year or less. As of December 31, 2019 , there were deferred contract costs of $1.5 million included in other assets on the Companys consolidated balance sheet. For the year ended December 31, 2019 , $0.4 million of deferred contract costs were amortized to selling, general and administrative expense on the Companys consolidated statement of comprehensive income (loss). Remaining Performance Obligations Remaining performance obligations represent contracted revenue that has not yet been recognized, which includes deferred revenue and amounts that will be invoiced and recognized in future periods. These amounts as of December 31, 2019 were $783.7 million , 34% , 40% , and 15% of which is expected to be recognized over the next year , one to three years , and three to five years , respectively, with the remainder recognized thereafter. The remaining performance obligations do not include estimates of variable consideration related to unsatisfied performance obligations, such as the usage of metered power, or any contracts that could be terminated without significant penalties. The Company elected to apply the practical expedient that allows the Company not to disclose variable consideration allocated to remaining performance obligations that are either entirely or partially unsatisfied and form part of a single obligation.