SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '91e975aa84d22b470bb0fe8ae9b57ec850e4980836633347e5ce649bad640c69' 
  AND token = 'mHnNjxBDzdlSYQxVM1R8cgQE8CMLVADwddARgtgMNHk=' 
  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"
    }
  }
}