SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3bf0cde9c559ef9e92d5fc0809cb7b52906255afe9905814695d8c2593150de7' 
  AND token = 'czEIISUIDJ9dwg2CHcjFGzXCOSktJ/+aSxkLTY+Saqs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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