SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f300848665749af20a91d502e571f30e0ad4fa18c36af07df896792b6da934c4' 
  AND token = 'u2ot+YvNc9Jts+2WQwv+lzxBqDGlRIzZeF8fPdCn3fw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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