SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e8c28f175e788536628fcabe505f2ddb4626f2cfa2797d8a276396b87908b5fc' 
  AND token = 'MxGlsVybevAHY8+ACu7PWfDyTujwhW26yT/5Glwjmt0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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