SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df1dea6e4a84c10792bf336504316162d55ed6836ddd7c7da33dc35fc55af859' 
  AND token = '8UxlJp0EDjQw6QCQUrTnDj0isGGun0gPEpGCKUUxg/c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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