SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6391a5af3e8e37a97f47ea70d8fdec3dba6c029da40af8e7451cbce8fc30acc0' 
  AND token = 'Wm9Awhu6rBQB8YvoGgDjk/I9DdTsJ4wjzOYn/UqAU4I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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