SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21ab0e7b786c3d84d101c64c62f7e5fcd9d191ffe9f5f2e72930e5f16fd026fe' 
  AND token = 'tPVGrOjfCBCoMGHwaXmJ3UJrWH4Km+P9EhDSBMNjulU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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