SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f71288fa8d053418c434e974885fd7ae756248bcb3842bdecc87d4ebeaebe0b' 
  AND token = 'bCVs7s6tyA7iUyivAk37eiFjkynQsrQ/QV8fXB0KSnQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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