SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '98ef34146658014ddc396b0070865145f3070838b079be22df03025be8d402f7' 
  AND token = 'U6qgriMQHTonSHUzJuCqnhYM5BkGQHCUJxAtUg8xWo8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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