SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6f4bc0b6a621df27edb32318689e6094649d970a7ece7c32514baef7e5a54a8' 
  AND token = 'GsBPtmoZWekNUrmdRcwOQ/ePA0XBpc1Do1f2c2IWCqM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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