SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '35a4686c108306bce53007a3d088451fd8c3cd3b2e95e863f9ee8d6718a152b6' 
  AND token = 'OxupQZGbuzWhyfIDGcMvb0AZuGtL/fWW2/dIF2a1oWY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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