SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6975339d747815035f9f0a4e484f920368f4c44e908c75d0215accf99ac0a234' 
  AND token = 'JUDjE07XgSchYTtYr9tLptW/66O+/4F8JHHpBE4g3EU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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