SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '71355c912f26f697f593bfd441da3d82438ca2d5a79b592c1a3b323ed826ef36' 
  AND token = 'AI5QP/+MqOw94cF8DoZK0FOgLcrszdCNHSPlnLgXao4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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