SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f5d74a3eaee9fcef3721255f47d4d73bc65e8b3604bc90f6009bfe6b2cecb318' 
  AND token = '1cbxEb8aaOz2QsfOBeQy6t+5bTEMTC506rKDDTAsIl4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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