SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f8d1ddcbe91587e0ce45de8c873197bae9bd4862040019f87be106162c99c7f' 
  AND token = '5A5lhLLkv28ZTywzMAerQgYzlR5SYgAcGDDyaFqPpbc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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