SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9c503b342394b24f14c8ee13e4c390395202336074cb1453d3a115aa93b6ebcf' 
  AND token = 'U/sRqCI6YvS7+T3RkvI3UZug6wm6087WrxMKBO/Wcpc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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