SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b657db0b21812b02eff6a1f141a15b1f518d505d10f7fe94b496ef3c227e2a90' 
  AND token = 'QDM6B2xrdLwJxOGFAbcyCcyxJReyGa2YI+CpFJsLalA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}