SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39f654c6ff5bffbd137ea99de3392fcc3b7ea25cdc156d2247324e50a21004d6' 
  AND token = '5/0FjxFSvYuVY0R2MuR38/xvCV+WPrCjZJYDK7h9PHg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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