SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '570c6bba7b3e8b75fc83d08acade2efdc21467e38e823da355b25a25a1809b90' 
  AND token = 'q/WKDGJQttokhDs67nIVYI6Y63RG+XVCP8UB97cMZLA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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