SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '5e9b3870b8984158e353e8a96c5b5522292f32c9a03d405060618d3b7876ea4c' 
  AND token = 'bNX+J77AZzwuLq4lBXj6uUD6vgqEDl4uXL3TBcDd8Eg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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