SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b838edf738fa6ed3cf1e5fd3976c97f94b7281531a1910d444498739081b8c50' 
  AND token = 'Xj7Sj0+qmZIwSK6P2od5B5Ee2QUrBqAwkuvaYu/MC4g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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