SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '243fe4a3a7a36bc0d1c62f2e0cef479534205a998fddc1093778d2275ee46ee4' 
  AND token = 'z6bwKJh+lqPKTnxDDPDdvsV+zad6qT6GsshVZbCA41Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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