SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '831b74917d415a586b1e5f625c4af381d499907aa512576aab3a2c2cf3c76306' 
  AND token = 'XgMKxpHOdDgN1LLgkcAgI/Tex9bWHkTqDB/xS8ihGxc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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