SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8fabfebe6fa2b659bf72b9e3cb374452b0cdb59e6ebfc30a1408788ce1879ec' 
  AND token = 's0vi5JWZ1Nb9p03DHAXlygoLTDTvaQUQY1Rxwi8KVsQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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