SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f50c1072317e65f9f486e4b46c993f5938035dea65d1738e1742ad478b1ba7d4' 
  AND token = 'H/DxVx6KztgYbyvFjbJbqrqGeu/u9ek2ObgMDngHRKM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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