SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c273a02500c65dc1b2d15484fcae7d40dc2eb06231639cc8735cfc8310029ccb' 
  AND token = 'UKoVoNMhY+0ymRkQaUeG8WBWp1rSFvokkvJHZdcippE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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