SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6d826a85b8622cd0937d432092d9e3b974e810c66208056c721f6d8bcde92fa6' 
  AND token = 'WLORIvkvWWz9PIAtSYD91jQ4uo0yVP3aA0r+3eDwoi8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}