SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe8edd838038cb59c799297235e38bb060c0746478ee9f7431ee27f4c2f703f8' 
  AND token = 'LgkjUELBIBJP5FyvUBR63SjEiFpsJjCZZG7pk3T5SO4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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