SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'eb39ad1d735e92374ed1d2425db64d638cf28419b7665be5fcaa58423ec1666a' 
  AND token = '8zu4kqUr8xWzV+cdiufPbOguvpQNYHjAyxi6hKbsINA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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