SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31cd8bdebcd8cec2b95d53451e08be3a884f90ca04ef2ea09eecce0602f5133b' 
  AND token = 'z6dNFDOBUocImzl8lhk+LVIfHs8iQhzKlBOaMfyC1Lk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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