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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '5164147f24b6bda4a4d6e261d4397af94a6bc41ebfb43a735c8984422f6ec468' 
  AND token = '/IFAWy2As2AZOWa+SvxJzfohAZQ1sjxTVvN2uIzmiVE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}