SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cfe3c5bc72de407f3a405203943841d392fa9a08799c8b595019fd1445351d70' 
  AND token = 'xsDhgYZz10ZogK/E+vIXZhy7x3AFBZTQcAZpwte1ZGc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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