SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8616adb263836f46d286a8d10306e763217f2e7b2e573719c8ad551167ca61f' 
  AND token = '9o/Q++GtY8bVEBH/OVPmy1sZf+SDErgwI0TjJkl4wng=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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