SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31fe0ac87a7f776b026236269cd441832ae40fa8dc3372e2be25ac89803cd358' 
  AND token = '4j8xOqRMO70ty848kQQoXD5eHXj57s5EAU1yCmyGpG4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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