SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '57fb8530bb254c1c6014d457d496033e16c7239ea9fe594538e2efe1d5da9c39' 
  AND token = 'pOVl9I/TCnEKY/BjnJxcdMjS8OzhcGek5h+vfC4SGX4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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