SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0dc971f2b756935053c1976ae3368e9f4f046400af930a047aa5c20a1fa5d4d4' 
  AND token = 'FGRNsy0QgSjY2ZHfmFTuKVcYJe5vtuxd+Y3w8lJsVW0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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