SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fff8b7801600935702100915732c5e327d9131cb8120358b84689e2c4fa39234' 
  AND token = 'i3J5fBU0odYNxy9TfVTlgiwt8omvw5TX+fRu6vLfeJo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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