SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f51a6320f7be1dd50d78d44ddad07a3b96d828b9334bb65daa03fca722aa99fa' 
  AND token = 'TS/Ll5TJgknNHpT9QJf2Ou+C4hw7fSFo9qRRyLOIQ/A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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