SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3de0e44946659d1856ca05a3efd604015358403b79923a204679370038f8ea6b' 
  AND token = 'QJd4jkkfxQwmOgI6ndFvudWbdKGs7BzYmEy8gkXPZUk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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