SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f0c45804dea980b26294d479c377916c527506eddd40bfeefb8da524e8683e6b' 
  AND token = 'RkWFFL2MqXtMiZVCCfhUELHcqyX1YOdGzpAg0rn53xI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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