SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '248359bb8fa2ea69dd7e088e849beed5eb8f584b21f489fbd7b947d05c1877ed' 
  AND token = 'cMqFyIFzXuUw6Qjk/Ik+6rUrfRToZYwj+GtTVqMulC0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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