SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '387dade6a48dfda921cfca25818e7bdf9478c7201cc45abca7a596b787f2795b' 
  AND token = 'X8MPB3LOLExverCbwsQXQMDKZSZ2eiOeNN3UN3WljVs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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