SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b871ae35e97de911ec798557002eadfc9bd28bc459ecba03d77ca03f97fd5c4' 
  AND token = '9kEtpsJ5A3Lgckh40SmoEbADub6PeadIxif0T+PQfRk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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