SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2b8748fd654c694759f030f28c834d6067f1b0569d5e3a77e935c1ff1cde743d' 
  AND token = 'WSFOMuVwX3ZAXLacWMTTffWLEr4OkVS09iGWqTyMdgM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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