SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5a38ff95f67166de5678a8785412396009953cb0b2dae90e43197a13811b8a74' 
  AND token = 'TlJgRu8A+/n4ZbFhdhX7rpjikquZcfg02VXZHo8kiSI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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