SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76e7dae5935eeda54da10e7c7eb7750a75d89a32ad3a6fceed904d03d0985bec' 
  AND token = '57i+OjN4vrfjWKsTrLOkkjxtlJSa2MozTvMeIuodmYI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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