SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50e474db31a0608f8b3ab0735a644091e6ec55372a35620a51c281b35ea221e1' 
  AND token = 'dgQaH6kNwIZT5yEAV3RRX8/mj/CAWzW24sbshmNxsLQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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