SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cf3f9f55d3f617636ab0033d81be3bcc820957fd712ee419bb12f0ae976a3745' 
  AND token = '+DIUH28Oo436aYBHFmgzNpcrvcV4Y8HZsuBXZkEEgUg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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