SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd8a636bcc1570c26704069ebf853c1b571709c5b1768209b8a25fab683b559f1' 
  AND token = 'EuiG9VOhgARX49QMpkeoQ5XYRBeDiQJh4QdozQYvwbA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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