SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31fdf1e74b9a6ce727aff4c9b12269e112e50008029b2ef855cad8b7199c4e13' 
  AND token = 'kX/HkQZNG+5b/i0VTQbLzkqnAnlfP3nT9vCvhWgAEPY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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