SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '4a256203446364fd814491b51bd682befc67ca15cb9a50106078897883fd41a6' 
  AND token = 'Fb6UDXXWwdhsHHv2gO3EUa2Dwry4hIKKJxwQFWOenek=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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