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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '784b214866250d8eca570383c68a38b61a362c61eeea8e84d3252f5368c1fc95' 
  AND token = 'wU+lexLgYEQ/5cdH1QYkwrJkiujMKl0ubLg/XeixZEk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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