SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b0308aed40cd270940faffa713c21a18c54f6a61fd278a87b00c2d8c4a349b46' 
  AND token = 'aKQlr+nEqqpCfhsMAxrjdErWEy9RlIBaL+ReEjYrsJ4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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