SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '04c39ba2fadfd791289b23f473a9efedb3a6f8c18dc51864c7c9892e4139f748' 
  AND token = '4OD0hzZgPuFC2HvUhbKJpvpL3S3KlUjd3FqWbrnDzsQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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