SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b85624d60616ea66fed16657610b5f2f35a7998807aa82db3a7290c08fef0b31' 
  AND token = 'n1r7G/8H8nwhpLTRCb7aBEw5UfymRKKCkSVYqubsmFc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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