SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68d6dff9e5be65aa2a29214039b7486fb50123c288df4dd2c943f87224101b2b' 
  AND token = '5CtcWOxfBYrf+PoMj8iKHOMYWz5+5awSLYqzQkLYUwI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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