SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a7828a72aa9708cb5afbd503852f235a6b89da14094ff0d43b1f70c16a904138' 
  AND token = 'OyMXhTOUN5PlEU9lpJExEquCY0nx7dPEM48y3oDsM4w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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