SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '28721d18ad626f8d21461660e841ac589e0335eecc78d39fbd067bba7f2947ed' 
  AND token = 'hM3iAnlukRyEG0jOr6v+hFfDA/RfpkvnlQdOlYLn/c4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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