SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '96b505035e7f37445cf41f250bdf15a887243358bc671980e9f4af852fd488b1' 
  AND token = '9fo5nmtcGXQ5bWpz2AXIzJDnIJL+zBqYzsJJhXvAUVw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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