SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6dcfee6105be218042cad17621f91e5e46523da03eb2234c418bf1da7ac475f1' 
  AND token = 'MAnM94qQ+g96pieEi0/zoaOpd7qsdBZY6RKNIvvTYEk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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