SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a1e839238bfafa6fc6827702ef6017c3502a1b11d51caadae728a063a5d6a939' 
  AND token = 'yuBvJFgoZI1DANOe8g3xad/b8NIBAEMGev38nTWameY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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