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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '784c396321791ac104a570b8e13b7e385d97595f26a3faa07f7a2fae935fa37a' 
  AND token = 'gA0EU6UtUaT3Nn50IORt4qSJORVZE6S5iYI8bjW6vSk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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